It depends on what kind of computer you want. If you want a speedburner, or something that you can upgrade for several years, now is a horrible time. Intel is moving to i7/x58/DDR3 by the end of this year. AMD is moving to AM2+, and will probably follow the jump to DDR3 sometime next year, or possible a bit later then that. If you are looking to buy something now and use it 2-3 years down the line with minor upgrades, now is a horrible time.
On the other hand, if you want to build a decent computer capable of handling games for years down the road, now is a good time. Intel has just released the 5200. AMDs quad and triple core CPUs are between $100-$125. Four gigs of DDR2-800 can be bought for $80. Harddrives are cheap, and AMD/Nvidia are locked in a graphics war that is only making me smile more and more. By spending only $100 on each part, you can build a good gaming system for around $800. (some parts won't be $100, through the extra cash into a better video card.) In the end, it depends on what kind of computer you want.