Early US only kindle 2s were Sprint-based. Later ones used AT&T. I also have a Sprint Kindle 2 (the one in the photos; that's a DecalGirl skin on it). I get a signal just fine on both... they're just a bit slow to lock on.
I ordered both Kindles on the day they were announced. This one came a day early; the last one came on release day, I think (I'd have to dig around in my records, but I'm 90% sure it came on release day).
I don't plan to get a skin for this one, at least not as of now. I'm also left-handed and the attachment points for the case are on the wrong side.
I have a pair of kandle lights. One is white and I used it with the Kindle 2. I passed the K2 and kandle to my fiance to use, and now I have a black kandle light for this one. My only complaint about the kandle lights is that they use cold-white LEDs and I'd personally prefer warm white.
The K3 has several font choices. I ended up tweaking the options further later last night and I'm still using a serif font. I went back to the normal font, but tightened up spacing a bit.
Gave plos.org a poke, and planned to just take a pic with my phone camera as I did yesterday, but the browser is slow and freeze-prone with a bad signal as is the case in here. I'll try again when I'm at home on wifi.