[MsAstoria]

As a former Sony 505 owner, I had no trouble transferring my non drm books to K2. My non drm books were in Epub format and I just loaded them up on Calibre and "converted" them to mobi, then transferred them to K2's document folder. I actually had all the books converted and sitting in a folder on my desktop while waiting for K2 to arrive, then just transferred them directly by drag and drop to K2 document folder. Painless! Seriously!
I really liked the Sony but wanted the added features of Whispernet wifi so I could use it for email and web searches when not at home. I really like the built in dictionary too and even use the text to speech for having books read to me while I am doing other tasks. The K2 is really a cool device, a mini computer for sure.
As long as your books aren't drm secured, you can convert them through Calibre. Another note, if you have multi format books that you bought on Fictionwise, you can go to your account there and change the format to mobi, then all your books automatically changed over and you can download them to the K2.
If you aren't familiar with Calibre, there is a thread through this forum. Get it even if you keep your Sony. It's very cool, free, and you can download news feeds and custom feeds to your unit.