I've purchased 5 Sony Readers and only one has failed.
I've had three different iLiad's and they've all failed.
Reader is a local (inside US) repair/return, iLiad is a return to Germany and I've been back billed by UPS $104 for shipping to return one unit.
The Sony has working power management, you can slide the switch to suspend/unsuspend it and it responds in seconds. The iLiad needs 10's of seconds to turn on/off.
You can legally purchase from a collection of over 11,000 ebooks for the Reader, you can't for the iLiad. Yeah I know, you try to convince yourself you'll only read PDF's for work, but then you download
Teaching the Au Pair to Submit from the Sony Store and your fate is sealed.
For me, the near instant on/off has been the "Killer App".