FUD Zilla reports sources close to NVIDIA believe ATI's Radeon HD 5000 series isn't making any big impact on the intended market because only very limited quantities are available:
Sources close to Nvidia believe that ATI is not shipping enough Radeon HD 5xx0 series cards to make any big impact on the intended market. Nvidia's pride is hurt as ATI is the fastest kid on the block, but Nvidia still insists that its sales are good and that it sells everything it has.
It appears that Nvidia had sold all its old chips and because it wants to clear inventories before Fermi comes out, it plans to keep quiet until the launch date. It is important to keep in mind that Nvidia and ATI are both ordering from TSMC and both firms know many wafers the other gets.