My mom just won a Sony T1 in some employee contest at the library where she works. Can't compare it to the others since I haven't used them, but the T1 does seem to be a good device -- lightweight, rubberized back that isn't going to squirt out of your hand, WiFi-b/g, USB charging, micro-SD expansion slot, etc. A Sony device that gets everything right and supports mainstream standards -- what were the odds?
Didn't spend much time with the software interface myself, but apparently, with a little help from my dad, she already got it connected to their WiFi and tinkered with some of the non-ebook features so that's a good sign.
Abacus Model 2.5 | Quad-Row FX with 256 Cherry Red Slider Beads | Applewood Frame | Water Cooling by Brita Filtration