I have the 505 and i love it!
Really easy to use and no problems with it at all. I've also bought the optional light for it as I read before I go to bed.....
Most of the 'books' that I read are all from torrents and I also use it to read manga (JPG's converted to ebook format).
Check out
www.mobileread.com for opinions on different readers and hacks and tips.