I've been very happy with CfE / Nat 5s but there again, ds is at a school that allows 8
The work he's having to do when I'm allowed to see it looks to be of a high standard.
It seems to be giving him a good foundation for Highers - in Maths, the class is starting the Higher curriculum in January and in Georgraphy, his teacher has been teaching him the different techniques for answering in a Nat 5 way versus a Higher way. And his English teacher just pushes them hard full stop
have I mentioned she's scary? 
If ds had only been allowed to do 6, he'd have dropped French (wrong, wrong, wrong
) and Computing Science as the other 6 were subjects that he's passionate about and/or which he needs to keep his options open for Uni (Geography, Physics, Chemistry, Maths, English and PE). I'd have had to fight with him to make him swap PE for French - but given he wants to be a professional rugby player and he does have talent I'm not sure that would have been fair.
As MyOtherUserNameIsBetter says, the Higher Education institutes also need to adjust, as they still look at the Highers sat in a single sitting - and CfE seems to be assuming that people are doing 6th Year and/or can do Crash Highers which puts a lot of pressure on them.
By narrowing their choices, you run the risk of pupils disengaging if they make a mistake in the subjects they chose - or not being able to do the ones that enthuse them.
The weakness of CfE seems to be the wide range of ways it has been implemented. Ds' school has taken a flexible approach and has technically breached some of its principles (moving from the full BGE a year early).
On the plus side, in theory, the BGE stage more pupils should get credit for what they have managed to achieve.
When I did my "O" Grades, I'd been allowed to drop PE and RE in S2
: that rightly no longer seems to be an option, as both PE and RME are compulsory at least until the end of S4.