I wish they would do this with more games. Give it something like a window after so many years (5/7/10 w/e) then just release them as free. They have made all the money they are going to from it.
I bought quite some games which are running perfectly well on my notebook with integrated graphics. And since the prices are low enough and I want to encourage this behaviour (DRM-free, tested), I happily pay the publisher of these old games.
EDIT: MechCommander was released as a torrent. Microsoft (you know, that Microsoft) owns the IP.
A game via torrent? It's probably already been "released" for them...
In fact, Commander Keen, a game that was released by iD Software 20 years ago, is available on steam right now for $5.
Naturally, there should be some drop off point in sales where the PR becomes more worthwhile than the couple bucks.