Alot of the new games are taking advantage of pixel shader 2.0 / 3.0 capabilities in larger and larger quantities, 2.0 is very frequent in most recent games (Mandatory???), 3.0 is slowly making a apperance, but should become increasingly common in the future. The graphics cards of the future are definetly going to need pixel shader 3.0 support, so if your buying a card today, think about tomorrow.
Asus p4c800 Deluxe,1 Gig Mushkin PC3200 Dual Channel Level II V2,Pentium 4 3.0 512k 800fsb HT, Thermaltake Xaser III, Thermaltake Spark 7+, Sound Blaster Audigy2 ZS Platinum Pro, eVGA GeForce 6800 GT