biggest downside: keys are very small. my hands aren't huge, so it's not a show-stopper. It's also not exactly lightning-fast (hah!). Actually my biggest headache has been the wireless router at home, which still misbehaves with ipv6 DNS
It's also running a UI called "Sugar", which is (I think) gnome-derived, but is quite counter-intuitive for someone (like me) who is fully-acculturated in the model of desktop and command-line. On the other hand, it's a well-thought-out interface for someone who's never used a computer -- four "layers", representing "neighborhood" [network-connectivity], "group" [sharing and joint activities with another PC], "Activities" [applications active on this PC] and "Activity" [the current app]. All four layers are available via keyboard buttons, which is handy too.
It's not that hard to bring up a command-line, of course -- and under the sugar is a stripped-down specialist RedHat install. Apparently there's a how-to on "upgrading to Debian" but I'm willing to be gracious and give this RedHat/Sugar combo a chance. Also the OLPC project isn't supporting this hardware with Debian, so I'll hang on.
battery and wireless reception are flawless -- in addition, when I'm writing on the bus, as I am now, I can turn the LCD to reflective mode and the battery drain drops to near zero, since the big electric draws are wireless and the LCD bulb (or perhaps the speakers or CPU, but writing doesn't seem to need either of those).