I read about this a while ago, but now it's live. You can download and play Planetside completely free until the program ends (March 24th 2007). Players will be able to play pretty much the full game, but will stop gaining experience at BattleRank 6 until upgraded to a full subscription.
A few of us gave this a go early on and it was good fun for a while (I have particularly fond memories of mine and Pogs driving 'skillz'

), but I think the few of us playing would find it a little frustrating to spend an evening taking bases across a continent, only to log in the next evening and find them re-taken.
Well worth a(nother) look at the current asking price if you're at all interested in massive team based FPS battles
FAQ for Planetside Reserves program:
http://planetside.station.sony.com/news ... th=current