After reading the smallprint for using a Kindle a few years back I used to be vehemently anti-Kindle but now I don't feel 'tied' to Amazon at all.
I'm not bothered by being tied to Amazon either. I've never found a book that I wanted to read that they didn't stock and their prices always seem competitive. I just love the way that the Kindle Store works so easily.
I can't remember the last time I used the local library (over 15 years probably) so the lack of ability to borrow books isn't an issue. I've always thought that if a book is worth reading then it's worth buying.