Microfiber, yeah, that's a good material. Almost forgot about that. Worked for a guy who swore by them for glass. I can take them or leave them, though they are a little better than regular rags and never leave lint behind.
I don't know if scratching a mirror should be any kind of worry. CLEAN cloth or paper won't ever scratch (but something with a grain of dirt on it sure might). I think as long as you don't fling things around, slide your spray bottle acrosst it, or go at it with something scratchy like a scrubby pad or something, you'll be OK. (Best way to get grime and stubborn dirt is to saturate it and leave it for a few minutes and wipe it off. Or Goo Gone or somesuch. I've used single edged razor blades to get tape and the like off with nary a scratch, though you may not want to do that if you're deathly afraid of hurting a mirror.)