The idea of buying a cheap reg for a few years, then selling it, and repeating the process is interesting, but not best suited for my circumstances because I've been mainly diving in the Philippines on vacations, and over there reg rental costs about $2 per dive, so if I wanted a cheap, but reliable, low end reg then I'd just keep renting.
I'm more interested in getting something that's better than the rentals, that I could use everywhere for most types of dives, and which I could either learn to service myself, or have it serviced for cheap, so as to make it cost effective in the long run. There's also something tempting about owning your own equipment...