Yeah sorry about that. :)
It is possible, but is only easy if you made /home be a separate partition. Despite my best efforts, this isn't the default.
You don't have a lot of files yet, though, do you? I think the best bet is to boot into single user mode and copy the contents to a USB memory stick. That should be easy.
You'll need to mount it manually -- plug it in, wait a few seconds, and then type
dmesg and note the device that it says was inserted. Then, mount that with:
mount /dev/sdc /mnt
replacing sdc with whatever dmesg said. (You may need sdc1, depending on how the device was formated).
Then, change to the root directory (
cd /) and run
tar cJvf /mnt/mattdm-is-sorry.tar.xz /home
and when that completes, run
sync; sleep 3; umount /mnt
(The sleep is for superstition.)
The reason for tar rather than just copying is to preserve the Unix metadata, because the USB drive will be FAT formatted, and we don't want to mess with that right now.
Then, once you have your system repaired (I still recommend the F15 alpha!), you can extract it with
tar xf /mnt/mattdm-is-sorry.tar.xz. If you do that in
/ as root, it'll overwrite everything in your new
/home, so probably the best thing to do is boot the new system into single user mode and do that first thing.
Oh, and this time, while you're installing, make
/home its own partition. :)