I've been very happy with my Jornada which I bought about a year and a half ago (on eBay) for $75. I was happy to read about the aftermarket batteries although I'm satisfied with my current battery life--on other PDAs, batteries have been major issues (I'm on my third with my iPAQ.)
In terms of Wi-Fi, I've had success using open Wi-Fi at hotels, the college where I teach, and in restaurants. No success with connecting to my own secure Wi-Fi (although it supports at least some encrypted Wi-Fi).
The screen is big enough that you can read PDF files, and the (old) version of Internet Explorer works well enough for HTML formatted eBooks.
I actually use the Jornada primarily as a writing machine (although I have read 6 or 7 books on it). The keyboard takes some adjustment, but it is possible to 10-finger type with it). I've written hundreds of pages on this machine as I use it during my commute on Dallas's light rail.
Because I don't synch, I'd be interested in any insights on how to load Mobipocket directly via the CF card.