McBrain and Eric,
Via an external drive, I use Time Machine (TM) on my iMac but thus far have fortunately never needed to use it in earnest. I've played around with it a little, though, and myself have wondered from time to time how it'd be possible to restore just a single file or group of files.
Okay, so let's take a general case. You open Finder, start TM and then pick (if it's amongst the dateline at far right) the date/time from which you want to restore. Then on the big bar at screen bottom you click Restore. This presumably then gives you the state of the machine that you require. But then what do you do if and when you've found from it the file/folder you're after? You presumably wouldn't want to then stay in the historic state you're in; you'd want to go back again to the state the machine was in just before you did the restore. But clearly doing that would simply undo the file retrieval just performed.
So, is the only way of dealing with this to take the retrieved file/folder and temporarily copy it to a non-TM drive of some sort, eg. a USB memory stick, and then, once back in 'today's' state, copy the file off the non-TM drive to wherever you want it to be on the machine?
Something else I've puzzled over is whether TM only ever restores the slice of the hard drive's contents that you select and see in the selected front TM window, or whether instead TM restores the entire contents of the hard drive (or the whole of the OSX partition, if the hard drive's been partitioned). In other words, does TM give you each time a backup of the the whole of the OSX partition? My gut feeling is that it has to be the latter, as the user will in theory need to restore anything from a single file to a complete state, from within the OSX partition. I've never found any publication on TM that's ever explained this.