We have just bought one from 'the unmentionable' company , but don't yet have a baby to put in it, so can't really comment.

However I just wanted to second people's comments about getting it professionally fitted. We thought we had it kind of right, but it still moved around too much for our liking... took it to a pro for $35 and the fit he achieved is vastly different to how we had it. Turns out we needed a special part because of our car. Initially I didn't want to spend the money, but soooo glad I did. Good luck with your hunting!