He does have a point even if you don't buy ATi cards. Ati's release is expected to drop Nvidia's prices.
Nvidia is supposed to be releasing a $300 GTS version soon and mid range cards in the spring or so.
Full versions of Vista are slated to be released in a mont or so I believe.
Worst case, buy either an eVGA 7600GT KO or a XFX 7600 GT XXX to hold you till DX10 prices drop. Both sell for around $100 after rebates and perform well.