For those of us with OLPCs,on the chance that y'all're tracking the "joyride" active-development branch rather than the release branches, note that recent joyride branches come with no activities, meaning you will have no applications after the update. As you will also lack the Terminal application as well as the browser (most of us use the Browser activity to install new app bundles), it won't be obvious how to get them back, and the official documentation suggests putting them on a USB key. This is pretty uncool for those of us who upgraded to joyride over the network. Solution:
Swap down to a virtual console (control-alt-F1 - note that the F1 key is not labeled as such - it's the "network view" key), hit enter to log in as root, and change your initlevel to 3 (multi-user non-X11 mode) by typing "telinit 3". Then, su to the olpc user with "su - olpc" and start a standard X11 session with "startx". Grab xo-get, an activity-installing script, using wget, chmod it to be executable, and start up the XO desktop with "olpc-session &". Quickly, before any parts of that desktop start (sugar desktop components don't work at all well with traditional X11 Window Managers), do "./xo-get.py upgrade" to install the old default app bundle.
There may be easier/alternative ways to do this that involve xhost or running sshd.
If you want to find out when a new release or snapshot you can ask olpc-update to install for you is available, something like "rsync --list-only rsync://updates.laptop.org/" might be useful. The new interface with joyride releases is pretty nice (once you populate your application ring, anyhow), and some applications work much more smoothly. Power management also (largely) works now, and the network display/management is much more intuitive - it still tries to be more "intuitive like a pencil" than "intuitive like an assistant", but it actually succeeds now.
... presumably anybody technical enough to running joyride would figure this stuff out by themselves eventually.
Note that xo-get has a vast library of applications it can install (it looks like a frontend to yum). I am slightly weirded out that somebody packaged Inferno (a Plan9-related programming language, kind of)...
If anyone wants to find me on the community server networks, for now I have associated my olpc with xochat.org and believe my userid there to be pgunn.