Hi PolarMummy - I bf ds1 for 5 months, it was hardwork and painful for the first month, if anyone tells you it only hurts if you are doing wrong its bull, sorry but it is, but if you persevere it does get better and I can say for the most part, it is then very easy once you have got over the newness and soreness of it.
My main problems with it were...
I felt like all I ever did was feed him, (every couple of hours) and you never know how much they are having. Now people will say that is what feeding on demand is all about and you have to deal with it... well I dealt with it but I wasn't overly happy doing it, also I would find I would feed him and then try and go out and do shopping, once I had got him ready, myself ready and got to the shops, he would be ready to feed again, not all facilities are great and the number of times I had to sit in the back of the car are too numerous to mention so I found it a real chore to go anywhere. I was also never very comfortable feeding him in public, I felt too self conscious and couldn't master doing it subtly.
Also if wanted to go out for the day without him (and I did a few times) or overnight which I did when he was 3 months old it would take me days to express enough for the babysitter to give him but then of course whilst out he isn't feeding so your boobs get full and then painful and you have to end up sitting in a loo somewhere expressing, I just didn't like it and felt too bound and not in control of my body. It did enable me to lose weight quicker though ;)
Yes it is good for them, as in it gives them ammunities from colds etc, but that is only whilst you bf them. As soon as I stopped at 5 months he then got constant colds, and I'm sorry I wasn't going to bf him for the next couple of years, just to stop him getting a cold.
The main reason I am only bf'ing this one for a week is so that he can get the colostrum which is the most important bit, also dh will be around that first week to help occupy ds1. I can not spend the amount of time feeding this one that happened with ds1, with ds1 being 2 years old and running around and having to do all the nursey runs etc. With FF I will know how much he his having at each feed and it will take less time to do the actual feed, thus not neglecting ds1.
These are my reasons anyway, it is obviously different for every one