OK - this may be a bit long, so bear with me. 
Disclaimer: I am an NCT antenatal teacher.
Apologies for this EPIC post. I've been chewing on this thread all day. I'm going to offload but may try to come back briefly later and respond, if anyone has any specific questions or comments for me.
First off NCT training: NCT teachers come from a range of backgrounds, including teaching (me), nursing, midwifery, and other professions. There are a good number of midwives who are NCT trained, who teach for the NCT, and there are NCT teachers who are not midwives who are teaching NHS classes in hospitals around the UK. As far as the length of training goes - it took me 5 years part time, but other people manage it in 2. The training has recently changed and become shorter in response to the increase in University fees. Can't say I'm not worried about this.
Second disclaimer: I acknowledge there are no doubt some awful NCT teachers. I have met a couple. 
Some observations:
People's actual memories of what they covered in NCT, and what opinions were expressed during their course are hugely, hugely coloured (I use that word advisedly - my first thought was to use the word 'distorted') by what happened to them around the time of the birth. And women come with their own agendas, which are often far more opaque, to them and to us, than any agenda of our own we might have. And these agendas shape their memories of the course and their feelings about it afterwards.
When I attend a reunion I ask the clients to identify one thing they really wish the course had covered/were glad the course had covered, so I can consider that when I teach my next lot of parents. I also ask this question on the electronic feedback forms I send them. Invariably clients will say something like - 'I really wish I'd known something about colic/realised how weird I'd feel in the first week/known I might feel like I've been hit by a bus'. And I stand there and think 'we did cover that. At length. In detail. You had hand outs. Follow up emails with links to mumsnet discussions. And sometimes I think - "I actually used the phrase 'you may feel like you've been hit by a bus' and we drew a diagram of a postnatal body, flagging up symptoms and talking about how to treat them, and I saw the fear in your eyes and went home feeling guilty".
Note: I say 'stand there listening' because I think it's disrespectful to try and cover my arse in a situation like this. I've come to the conclusion that something about childbirth and becoming a parent blows every part of your life and your psyche to pieces, and they reassemble in such a way as to make everything that's gone before a foreign country, and that this is just the way it is. Not much lingers. Including what they covered in NCT!
I accept that very little I personally do on the course will stick and will make a difference. Apart from the friendships, and hopefully the message: DO IT YOUR OWN WAY. I try to make people feel that they have it in them to make the right choices (which will not all be the same) for their baby because they will love their children and do their very best by them, and that they need to trust themselves. I don't think this actually suits some people - they want to be TOLD what to do, because it makes them feel safe at a time when they are actually a bit terrified about the whole prospect of parenting. It's like they feel the course isn't worth the money unless it's really prescriptive, but if we are prescriptive then you can guarantee that some people will find the content useless and sometimes downright offensive.
As far as the 'natural birth agenda' goes - we are doomed which ever way we play this one. I have had feedback from the same course from clients describing the content as 'negative and scaremongering' and 'reassuring and realistic'.
One client I've never forgotten came to a course in a state of complete evangelism about going to a free-standing birth centre 30 miles from where she lived. She spent her pregnancy reading natural birth books and was quite preachy to the rest of the class who had all booked into the local hospital. I never undermine people's choices, but when we were talking about birth settings I made the comment 'some women find the pain of labour absolutely unbearable and those women will need an epidural to have a happy birth experience'. We talked about transfer rates from homebirths and birth centres. In the event she ended up on the labour ward of our local hospital. Her baby was born with a previously undiagnosed health problem and the whole experience was very traumatic (although with a good ending - her little boy is completely well now). I saw her a few months down the line at a nearly new sale, and she cornered me and said plaintively, 'why didn't you tell me how painful it was?'. And I couldn't answer her. Because I did tell her, and she didn't want to hear it! And I have no doubt at all that she's told lots and lots of people that NCT classes are unrealistic about the need for pain relief in labour - because that's what she remembers. But it's not what happened!
Would also point out that it's completely not unrealistic for the NCT to communicate to mothers that the majority of healthy women can have a straightforward experience of labour - even with a first baby. BUT ONLY IF THOSE WOMEN ARE GIVING BIRTH IN SETTINGS WHICH ARE SUPPORTIVE OF NORMAL BIRTH, AND HAVE GOOD CARE. And this, for me, is the nub of the issue. We give clients the message: if you are low risk (most are) you should have a good chance at an intervention free birth (because the outcomes for healthy first time mums opting to labour in birth centres and at home bears this out), but the reality is they will hear this message, and then they flock on mass to labour in settings where intervention rates are sky high. Because that's where the beds are, that's where they feel safe, and that's where the epidurals are. And then, in large numbers, they'll generally have births which involve a colossal amount of intervention. I regularly have whole groups where all the women are low risk at the start of labour, slim, fit, healthy, and where you'll see one normal birth out of six, with the rest having forceps/ventouse/emergency cs. And yet they've all gone into the experience hoping for a normal birth and being encouraged to believe that they have a reasonable chance of one. No wonder the NCT cops so much flack. We are being scapegoated for being the ones giving the message that 'most women can have normal births' in a maternity system which somehow seems to be making this impossible for ridiculously large numbers. And you know midwives are incredibly kind on the whole, and really hard working, and are with women at the most intense point in their lives. Understandably women don't usually want to blame them for anything. And they don't want to believe that their labour could have been any different to how it was, or managed in a different way which might have given them a better birth experience. If women are treated with kindness, and come through birth with a well baby they tend to be very loyal to their birth experience, no matter what. So they look back on their NCT classes as being unrealistic and naïve, midwives (who as a group are often eaten up with angst about the part they play in relation to the rates of intervention in the labours of healthy women) sometimes encourage them to view the NCT in this way, and some actually feel furious with the NCT for what they see as setting them up for disappointment.
Anyway, apologies for the essay.
One last comment: NCT teachers can cover anything they or the clients bloody well want in classes, including bottle feeding. There is no ban on discussing it, if clients have indicated this is something they want to cover, it's simply not a 'routine' part of the course. The only thing they - and midwives in the NHS - are discouraged from doing is demonstrations on how to make up a bottle, because research shows that parents don't retain this information accurately enough to do it safely after the birth. Instead they can discuss the issues surrounding bottle preparation, how to choose formula, how to bottle feed, and give out printed information showing how to make up a bottle. If anyone has had the experience of being told: we can't talk about bottle feeding - phone up the NCT and complain.