i've seen those little 12v micro mills and lathes and I almost bought one off ebay last year but decided not to after doing more reading on them. They're really small and not very rigid so they would work good on plastics like delrin or wood but have limited use on metals, some of the softer aluminum alloys would probably be ok, but the harder alloys or mild steel might chatter. What's good about them is their size and light weight, and they would be excellent for practicing on machinist's wax or someone could use it to make a part they intend to cast in aluminum then do the clean up with it once the casting is done. I was even thinking about getting one then filling those aluminum square tubing rails with machinist's wax to add more rigidity so it could process metals a little better.
They also make some of those micro mill/lathe/drilling machines out of all aluminum with no plastic parts for the structure, but they cost as much as a HF mini mill or lathe. It would be really neat to have one like that, but I wouldn't expect too much from it. I saw one kit on ebay last year that had all the attachments in one kit like a small rotary table, dividing plates, and a few other highly desired goodies so if someone is starting out and does most their work with plastics, woods, or soft metals, I'm sure one of these would do just fine on smaller items. I'll try to post a link to the all metal ones I saw last year when I get home...