- Currently clearing last of their stock. $20 for one, less in bulk.
- No open source hardware/chipset. :(.
- No proper USB port (USB host/client on dock connector.)
- Has hacking community (#zipit on irc.freenode.net)
- Fiddly keyboard (haven't used a Nanonote but wouldn't recommend notetaking on a ZipIt.)
We group bought 21 Zipits recently at my local Hackerspace. I just designed a breakout board for the rear connector (GPIOs, SPI, 1 ADC channel & the USB 1.1 client/host port) which will should be available at some point soon I hope.
I'm also one of the maintainers for the OpenWRT for ZipIt port, people have ported all kinds of bits and pieces. Some folks also run Debian and I think there are some bitbake-based distributions as well.
 Although so far nearly all of those are sitting on shelves largely unused. Geek impulse buying strikes again! :(
I have both a Zipit Z2 and a Nanonote and thus can compare the keyboards of those devices. I'd say the layout of the Z2 keyboard is better than that of the Nanonote. On the Nanonote many characters are on weird keyboard positions (with multiple modifier keys) and the space button is very small. The Z2 keyboard is very loud (clicky), which I don't like very much, the Nanonote's keyboard is not. Here is a little comparison of the two devices: http://wejp.k.vu/zipit_z2/ben_nanonote_vs_zipit_z2