Well, I won't be doing that again.
I plugged the Touch into my computer last night to copy over a few audiobooks. I canceled when it started syncing for some reason, but I realized this morning that it wiped my music. 🙁 (I know that you can sync or use iTunes Match, not both; but I didn't expect it to start syncing.)
I'll just listen to what I listen to and hope they add "Download All" to playlists soon.
Update: For now, I just turned off iTunes Match on the Touch, and I'm syncing it with iTunes the old-fashioned way.