I love my Kindle, no complaints here.
You get free 3G on it, so it's nice to be able to look something up (it has a web browser similar to a smart phone) if you're in the car or out somewhere. I don't have a fancy phone though, so maybe that's just a benefit to me. ;)
Also, Amazon has plans to make it so you can check out books from your library electronically. I think that feature is coming out this fall? I don't know if you'd be able to do that with other devices, but for me, that would be a HUGE benefit.
Hope this helps, good luck with your decision.
Edited to add link to Kindle Lending info:
http://www.amazon.com/gp/help/custom...527380#library