[cheesified]

Just stumbled on this while reading a review.

Why NVIDIA Did It

To understand the motivation behind NVIDIA's naming and renaming and renaming we have to once again look its approach to GPU design. NVIDIA continued to architect very high end GPUs and allow their technology to, over the course of 9 - 12 months, trickle down to mid range and lower end market segments. AMD stepped in and launched a very competitive performance mainstream part instead of a high end GPU, allowing it to windfall down to lower price points and market segments quicker than NVIDIA could for this generation.

Let's attach some code names shall we?

NVIDIA's flagship, the GT200 GPU used in the GTX 295, 285, 280 and 260, isn't available in a cheaper version yet. AMD's flagship, the RV770, is already more affordable and is available in cheaper versions. NVIDIA has to rely on its last generation GPU, the G92b, to compete in the rest of the market while the lower end GT200 derivatives get ready for production. Rather than continue to ship products with old names to vendors and customers, NVIDIA slaps a new name on an old GPU and hopes to at least provide the appearance of being just as agile and competitive as AMD despite being clearly caught off guard this generation.

AnandTech: NVIDIA GeForce GTS 250: A Rebadged 9800 GTX+