Well, I tried to take into account technical side, Sony is good at making HW and support is slow but it will eventually solve the problems. You're right that mobipocket is widely spread but I have a number of txt/rtf myself so that's not crucial for me. As somebody mentioned in some other thread, I'm waiting for this since I saw Star Trek as 9 year old and managed to build my SF library in txt/rtf in hope that some day will come to convert library to whatever format it takes. So this is probably correct in my case but not necessarily for others.
I still have one mp3 player from Sony which has served me many years. Software is still horrible, conversion awful and so on. But HW never let me down. This is little bit idea behind the reader as well: I don't expect that reader sw or format support will be as good as we wanted for couple of years to come but hopefully acceptable.
Secondly I have some weird idea/hope that Sony will find other distribution partners, connect shop is incapable of giving the right upswing in book sales.