I own a Sony 505. I basically bought to read books without the need to tote them around. This comes in handy when reading several books at around the same time. As for the prices of these reading devices they vary. The irex iLiad, is expensive at 699$. According to website you can draw and write on it and you can also read newspapers.
http://www.irextechnologies.com/ ).
As for the PDF capabilities, I stopped perusing the site when I got to the price! The cheapest one I saw was the Gemstar/Rocket reading device from Ebookwise, (
http://www.ebookwise.com/ebookwise/ebookwise1150.htm), which sells for 109$ sans memory card. I chose Sony because I could transfer PDFs to it. The only drawback is if you purchase ebooks via stores like Sony ebooks, Books on Boards, you cannot download them to your computer files as such. Rather, you have to download ereaders such a Adobe Digital Editions, Mobipocket, or Microsoft readers etc. However there are many sites where you can download ebooks for free. Two examples immediately come to mind, Project Guttenberg and Internet Archive. I believe that many of the copyrights have expired for these books. The only contemporary site which permits you to download the file directly to your folders is Lulu.com which is a site for self-publishers. I believe the restrictions imposed by Adobe, Sony and Microsoft readers are to prevent dissemination of the books to other who have not purchased them thereby depriving the authors of compensation. Like all technology, this particular field is constantly evolving, so many concerns in regards to visuals etc may be mute in the future, in the very least minor. I found that the Sony reader is suitable for my needs which is just reading books. I have not purchased a 'book' in several months as I can find most in ebook form via the ebook stores or the free sites which I mentioned above.