ORIGINAL: Michael Burke
Quite frankly, this setting has little "apparent" affect on the server. Setting to "Programs" simply gives session 0 applications more CPU cycles, but unless someone is logged on to the consoles (using session 0) regularly, it really has no effect. So if you want to be technical (and I hate to disagree with Jeff on this one), I feel the better setting is "Background Services" as it doesn't put any priority on session 0.
Anyone care to add anything?