Thanks for all of your responses, everyone!
I think rdenney really said it:
There are some really excellent and cheap 35mm and 28mm lenses out there in the M42 mount. As with short telephotos, I think it would be hard to find a really bad one, especially if you recognize the brand. With an AF-confirm adapter, you can probably get by for less than $100, making it a cheap experiment.
If you find you just can't focus it consistently, just put it back up on ebay and you'll probably get your money back out of it.
Exactly what I'm looking to do. I'd like to find a cheap 28mm or 35mm lens and play around with it. If I find I'm not into manually focusing, I'll put it up on eBay (or here, for that matter).
(OT: Or could be 'Rick "can't make up his mind" Denney' )
@condyk: I've heard great things about the Zeiss lenses. Thanks for the AF lens suggestions, also. I suppose I could just go for one of those and put this whole experiment aside. But now I'm curious.
@argyle: Thanks for your Zuiko suggestions, too (and you will be hearing from me via PM ). Definitely small, compact, and light fit the bill as well.