There are plenty of good reasons to be suspicious of frameworks in general, balanced of course by lots of reasons why they are worthwhile.
I use jquery now, and frankly within an hour of learning it realised that it fits the job so well that if it didn't exist I'd only end up reimplementing something very similar myself, only it wouldn't be as good or as cross platform.
There isn't much bloat there, it's very small and well designed and does nothing at all that stops you writing any javascript you want for specific cases that don't fit your needs.
