i usually upgrade my pc part by part, from 1998 - 2003,
started with a AMDk6-2 that gives me blue screen of death twice a day.. (was a heating problem)
went to a celeron, then to a AMD 1ghz, and now finally AMD1700XP
these upgrades were all done in 1998-early2002. but since mid 2002 - today, i haven't done any serious upgrades. only last upgrade that i did was bought the ATI radeon 9700 pro (to play C&C generals

) everything else in my computer seems to have stalled..
now i can't foresee myself upgrading any parts (except for my sound card - sblive) to a audigy2 platinum. but my only reason for this upgrade is simply to have the finest part avaliable in the market. otherwise, for performance sake, the good old sblive (not 5.1) is good enough for all mp3 music, game playing. and such.
i would agree with most guys here.. it seems that we've come to a stall for the average user. Even for gammers. there are only few good outstanding games coming out soon. (doom3) that really requires a system more then 2ghz and a 128mb video card. and those games won't come out till like end of this year or so..