The Sony Reader has no WiFi but has opened every Epub I have thrown at it. It connects to any PC, even to Linux, and shows up as external disk drive. You can use any shell you want to move files onto it. I have a (Linux udev) script that syncs the ebooks to the Sony every time I plug it in. That's not quite as comfortable as WiFi but I gladly pay that price for the freedom to download what I want from everywhere I want.
Agreed this is about my current experience with Kindle. I also download some stuff via the Kindle's rudimentary web browser over 3G. But, I've connected and disconnected the Kindle literally a couple thousand times via USB now, and its getting really really old. That is why I'd like some kind of ebook reader that will allow me to transfer ebooks by wifi. I can do this using my netbook, in all of MOBI, ePUB, PDF "ebook" formats etc, its just that the keyboard really gets in the way of the ebook reading experience. With the current ebook reader apps one cannot even use the PgUp, PgDn buttons to change pages! You've got to use the mouse-pointer-pad thingee to click on the GUI up/down arrows. So what I want is an ebook reader with an "unlocked" interface to wifi so that we can do the kinds of things that we are permitted to do today by USB -- but actually using the wifi hardware capabilities built into the ebook reader already.