Did NVIDIA need to release this card? - Yes and no. They ultimately needed something that sits in the same price range as the HD 4890. Having a look online at the real pricing of these cards, we can see that the HD 4890 does come in cheaper than the GTX 275.
The GTX 275, however, is really consistently faster, so does this mean it would be the better choice? - Well, honestly, not really. If you want to game at 2560 x 1600 the GTX 275 is just able to cut it for the most part, but if you've got a monitor that can handle this resolution then hopefully you have the bank account to accommodate a higher end card like the GTX 285 or GTX 295.
At 1920 x 1200 both cards are pretty playable in most games, so why spend the extra money buying a GTX 275? - The main reason is that you can run your games with slightly more detail.
At the end of the day, the HD 4890 is, for the most part, slightly slower at playable resolutions and slightly cheaper. What we have are two cards that ultimately represent the same value for money. If you can spend a bit more and want a bit more performance which will let you have slightly more detail at 1920 x 1200, then the GTX 275 is a good choice. Slightly less detail, cheaper but still playable at 1920 x 1200; the HD 4890 is the better choice.
What we would have preferred to see is NVIDIA drop the pricing on the GTX 285 to combat the HD 4890 instead of offering another new model. What it all comes down to, though, is we have a nice card here and Gainward has mixed it up a bit with the cooler. Now we need some OC models to see what the card is really capable of. There's no reason why when overclocked it won't be able to take down a stock GTX 285.