[a_ber]

Ken Rockwell как всегда категоричен
http://www.kenrockwell.com/nikon/d40x.htm

Bad News:

1. $200 more expensive than the almost identical D40: $799 vs. $599, or 33%!
   
   If money matters, you should put that $200 towards lenses, like the new Nikon 55-200mm VR or the SB-400, not on the D40x vs. the D40. Bouncing the $129 (list) SB-400 flash makes a huge difference in photo quality indoors, and megapixels don't. I've got a zillion photos of my baby Ryan made with a bounced SB-400, see if you like the quality compared to the quality you get on your current camera with the built-in flash.
   
2. Slower default ISO: only ISO 100 compared to D40's ISO 200. This can lead to images blurred from subject or camera motion or reduced depth of field. The higher-speed sensor of the D40 allows the excellent results at ISO 200 while the less sensitive sensor of the D40x requires ISO100 for the same thing.
   
3. Slower 1/200 flash sync, down from the excellent 1/500 of the D40. This reduces flash range outdoors, makes it difficult to get sharp flash shots of sports action, and reduces battery life with flash.
   
4. Larger files sizes clog hard drives, memory cards, waste backup CDs, and take more time to transfer, copy, backup and archive. You'll get fewer photos per memory card, which isn't much of an issue today, but waiting for all the other things is.

Good News:

1. Slightly higher resolution: D40x images are 3,872 pixels wide versus 3,008 pixels wide in the D40.
   
   So what? Like square footage, megapixels is multiplying image height times image width, so this minor increase looks impressive when multiplied out to 10 MP from the D40's 6MP.
   
   This is only significant if you're printing larger than 13 x 19" (30 x 50 cm) and larger, and even then, not very significant. I've seen 4 x 5 foot prints made from the 6MP D50 which looked spectacular; it's all about knowing what you're doing to get a sharp image. See also The Megapixel Myth.
   
2. Slightly faster frame rate: 3 FPS vs. 2.5 FPS. If you're shooting sports, I suggest getting a D200 with 5 FPS to see or feel any real difference. I notice no difference between my 2.5 FPS D40 and my 3 FPS D80.