I haven't done it, personally (AS), though I think I might in A2 depending on my timetable. I've had friends that take their laptops, and seen the odd person in lesson take theirs as well because it was easier for them to type up revision notes. Anndddd I've also had a friend just play games on their laptop during breaks.
I don't think it'd be particularly useful unless you've got a serious shortage of public computers available in the college. I might have seen a couple of people take a laptop to school in my sixth form but no more than that, there simply isn't a lot of point.
Wow, I never saw anyone at my college on a laptop. :P It makes sense why you'd want to, though. Just keep a really close eye on it if you do (especially if the area you're in is anything like mine)...