If you buy a D90, Nikon are currently offering a £50 or £60 cash back. PC world have got the D90 on display and maybe the D5000 as well although I didn't look for the latter when I went in today. I was looking for the D300s and the D700 which they don't stock as they are too high end for PC World.
Am I right in assuming you can only use DX lenses on DX digital cameras?
Most high SLRs are now FX full screen which allows one to use older lenses designed for 35mm which can be a real bonus if the mount is still the same although you obviously won't get autofocus as with a more modern lens. DX and FX lenses are not interchangeable AFAIK.
The quality of images taken on DX digital SLRs is now as good as full frame CMOS cameras which have a much brighter view finder and screen than DX cameras. Last week's Amateur Photographer did an article on just this issue and resolution at higher ISO for DX and FX cameras. Pro cameras such as Canon 1D Mk whatever and Nikon D3s use full frame CMOS sensors. Cheaper enthusiast digital SLRs have DX sensors which are rather smaller, but have software to compensate for lack of resolution and darker screen/viewfinder than full frame digital SLRs AFAIK.
For me I like the Nikon camera bodies such as the D300 or D700 for it's superb low light capabilities very little noise at ISO 6400 and the Canon L lenses. Unfortunately they can't be mixed.
Personally I would spend more on the lenses than the camera body although the body is still important. Don't forget to factor in the cost of additional memory cards, battery pack if required, leads that don't come with it, flash, filters and decent case to protect it.
The D90 comes with the Nikkor 18-105mm f3.5-5.6 lens whereas the D5000 with only the Nikkor 18-55mm lens. I liked the former when I twiddled with it in PCWorld at lunchtime. Though I put it down sharpish when security started to move in my direction

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