Yeah I have to agree with Remedy...
DDR is pretty sweet...but...
Games bottleneck on the Video card. I have an Athlon 550 with 128MB of RAM on a K7M...I'm going to buy some more RAM this friday (128MB is not enough for Win2000, 384MB would be much mroe pleasant), and a TBird SlotA 700Mhz ($75 shipped, how could I say no?) I'll overclock the TBird as much as I can...and seriously I expect this guy to last at me least another year if not longer...
I have a K6-2/350 second system (well it's my uncles) with 64MB of RAM and a 6gig hard drive...he runs all his office apps and stuff on it just fine. Sure my 384MB of SDRAM won't have the best office app benchamrk scores...but seriously...do you really doubt that a 700+ TBird with 384MB of RAM is not fast enough for office apps? i didn't think so...
And I'll drop in a nice zippy video card with hardware T&L and when HW T&L starts to take off that will decrease the CPU load even more...
Games bottleneck on the Video card and standard office apps have been bottleneck on human input time since about a P2/300 with 64MB of RAM (edit: or maybe hard drive speed...but I'm not about to go get a 10k RPM SCSI drive..I dunno about you

)
The only place DDR will show real world improvements is in workstation/server usage (especially graphical workstations which do most of the rendering work in software not hardware)
Will your game framerates go up? Yes...especially at 640x480...but will you notice it? No...we don't play at 640x480 and games are to dependant on other things. DDR SDRAM is definately better than Rambust...but I don't think we need either for main memory yet.