I also love, love, love! my Kindle. I have the Kindle 2 and it far superior to the Kindle 1. Yes they can be used for college textbooks -- far more economical and no weight. Also, Kindle has just issued an improvement wherein you can load .pdf documents directly to your Kindle. I have a User Manual for my Bernina software, Version 6, which is in .pdf format, and I can now download it to my Kindle and read it whenever I want.
I think they now cost around $250, but well worth the price. Downloads are almost instant, and a charged battery will usually last about a week, so you have to plan ahead for that.
Also there are plenty of free books. For instance, yesterday I downloaded a free Slow Cooker Cookbook.
They are such fun!