Both Nvidia and AMD have released a new generation of video cards set to duke it out at the $230-$250 price point.
Nvidia released the GTX 275, a mid-range, single GPU graphics card designed for the $229-$249 price point. Video cards based upon the Nvidia GTX 275 GPU should be available on or before April 14th. You can read Nvidia's complete press release (complete with plenty of marketing hyperbole) here.
...worst-case performance [for the GTX 275] is still better than the GTX 260 core 216 and in the best case, it can hit that of the GTX 280...
Anand Lal Shimpi & Derek Wilson of Anandtech.com
AMD countered the GTX 275 by releasing the similarly powered and priced Radeon 4890, which should probably be available by the time you read this. You can read AMD's press release (also complete with plenty of marketing hyperbole) here.
The 4890, basically a tweaked and overclocked 4870, does improve performance over the 4870 1GB and puts up good competition for the GTX 275.
-- Anand Lal Shimpi & Derek Wilson of Anandtech.com
Anand Lai Shimpi and Derek Wilson summed up their overall opinion with this:
"On a pure performance level the 4890 and GTX 275 trade blows at different resolutions. The 4890 tends to look better at lower resolutions while the GTX 275 is more competitive at high resolutions. At 1680 x 1050 and 1920 x 1200 the 4890 is nearly undefeated. At 2560 x 1600, it seems to be pretty much a wash between the two cards....If you've got a 30" display then either card will work, it's just up to your preference and the items we talked about earlier. If you've got a 24" or smaller display (1920x1200 or below), then the Radeon HD 4890 is the card for you.
Read the complete GTX 275 vs. Radeon 4890 comparison at Anandtech.com