is nikon D90 a good buy?  

Nikon D90 Key Features:

12.9 megapixel DX-format CMOS sensor (effective pixels: 12.3 million)
3.0-inch 920,000 pixel (VGA x 3 colors) TFT-LCD (same as D3 and D300)
Live View with contrast-detect AF, face detection
Image sensor cleaning (sensor shake)
Illuminated focus points
Movie capture at up to 1280 x 720 (720p) 24 fps with mono sound
IS0 200-3200 range (100-6400 expanded)
4.5 frames per second continuous shooting (buffer: 7 RAW, 25 JPEG fine, 100 JPEG Normal)
Expeed image processing engine
3D tracking AF (11 point)
Short startup time, viewfinder blackout and shutter lag
Slightly improved viewfinder (96% frame coverage)
Extensive in-camera retouching including raw development and straightening
Improved user interface
New optional compact GPS unit (fits on hot shoe)
Same battery and vertical grip as D80
Vignetting control in-camera
72 thumbnail and calendar view in playback

source:

from dpreview.com

I just bought a Nikon D90 two weeks ago and I just love it.
The kit lens is a very good lens to start with, I wouldn't reccomend that you spend extra money on a new lens unless you are a professional photographer.
I think it's a very good buy, if you have the money for it. The menu is user friendly, and it has a lot of interesting features to explore digital photography.
However, if you are not planning to explore photography deeply, and you want it only for birthday and holiday pics, I would reccomend you bought a D3000 model, which is quite good too and much cheaper.

the same to me , i am a newbie too ,i want to buy nikon D90,but i dont konw how is that , Have you buy it ??? and what do you think about that, is it good or bad??????