When I got it back, Apple had not bothered to clear out the forced verbose boot-up, and I'd forgotten how to disable it. Luckily the local shop cleared it for me without any further charge. Apple had also installed Leopard on the new drive for me, but they must have screwed something up with the install, because after I finished the initial setup/registration process, it would just keep looping back to the beginning. The lead tech at the local shop said this is typical, as they are constantly getting stuff back from Apple where hardware has been replaced and/or software installed but there is no effort made to make sure the machine actually works as intended afterward...kind of sad on Apple's part, but perhaps it's just an unfortunate symptom of their increasing user-base.

Anyway, I ended up wiping the drive and reinstalling Leopard myself, and now she's running right as rain. And also, a correction, it turns out they did not replace the optical drive, just the mobo and hard drive. Although the optical drive was unresponsive before I handed it over, it was an effect of the IDE controller failing, not of the optical drive itself. I also got a new (to me) 18" LCD monitor for the Mini, along with the aformentioned MiniStack...I should really take some pics of the 'new' setup sooner or later.