I actually sold my D90 to a friend who had a D80 and he has taken way better pictures with it vs his D80. He is very impressed with it. Sounds to be you are making excuses to not upgrade.
I'm a bit puzzled by this. How are your friend's images with the D90 better than his D80? Please elaborate.
I new body does nothing for composition. It does nothing for lighting. Assuming the same lens is being used, it does nothing for distortion or contrast. It's been awhile since I've compared a D80 and D90, but I'm not sure that the body change will result in a difference in sharpness (though it's theoretically possible that with a good lens the difference in sensors could result in an improvement in sharpness; I'm too lazy to look up the sensor changes that happened between the D80 and D90).
So I will go back to my original question: how exactly did your friend's images improve following the body switch? If he shoots in JPEG, then the difference could be chocked up to differences in camera settings. If he shoots in RAW then I have to seriously question your assertion.
Canon and Nikon WANT people to believe that the camera body is the most important element in image creation that distinguishes "good" images from "bad" images. It is vital to their bottom line to make sure that everyone feels the need to purchase the "latest and greatest" if they want to make stellar images.
The body is the least important component of image making. There are obviously exceptions, where you really need a specific body to create a specific image, but in general a body upgrade will get you the least bang-for-your-buck.
So what does matter?
Choice of subject > composition > lighting >proper exposure for the shooting conditions/image you wish to create > appropriate lens choice (focal length) > quality of lens. Obviously some will argue about this specific order, but these are the "vital" components. Format enters in there as well as a pretty big priority (small image sensor on a P&S, cropped sensor, full frame sensor, medium format, large format). Camera body is the least important element in image making. Better bodies usually offer convenience (easier to make adjustments without fumbling through menus). The ergonomics of holding the camera can be important. But for most applications that amateurs use cameras for, the choice of body has minimal impact on the final image. "But the specs are better. You are a fool. Objective data states that this body is better than the previous generation." Photography isn't about specs, it is about images. Sometimes the specs actually translate into noticeable improvements. Most of the time they don't. If you happen to be shooting something that would benefit from the better specs, then do your own cost/benefit analysis as to whether it is worthwhile to upgrade. But for most amateur applications, you won't see any real improvement with a body upgrade. Going from a P&S to a DSLR, yes. Going from 35mm to large format, yes. Going from one body in a given class to another body in the same class, probably no.
Lenses have a much larger impact on the final image compared to bodies, assuming the basics of composition, lighting, and exposure are met. A good lens will offer better contrast and less distortion than a crappy lens. It will also offer better theoretical sharpness, though whether this translates into the final image is dependent on the technique used when capturing the image and possibly on the limits of the sensor in the body. OMG, body does matter then. Well kind of. For specific applications it's relevant to match the resolving power of your lens to your body but for most real-world amateur applications this is only an issue on paper. How often do most normal non-professional people print at a size where this issue becomes relevant?
To argue that your friend suddenly started taking "better" images after upgrading from a D80 to a D90 is a comical assertion assuming that nothing else changed in the transition. The differences between these two bodies won't be evident in most real-world applications. Pixel-peeping you might see them. Maybe. I can't recall if significant metering changes happened between these two bodies, so that might be an area where improvement was observed. The D70 had exposure issues, but I don't remember this being the case with the D80.
It isn't enough to quote reviews on how one body is better than another. Cameras are tools, nothing more. It shouldn't be about the gear, it should be about the images. Most of the differences with current (or relatively recent) bodies are about bells-and-whistles that don't actually influence the images produced by the camera (assuming you care about the final viewed image and aren't obsessed with pixel-peeping or performance against test charts). If your creativity is limited by your current gear (either body or lens), then by all means purchase something that will better suite your needs. But really think about how your current setup is limiting you. Will it really be fixed by a new body? Would it be fixed by a different lens? Sometimes you might be better served by filters, tripods, or lighting gear rather than listening to the Canon/Nikon marketing machine. Depends on what you shoot. But don't for a second believe that a new piece of gear will magically produce better images if the real problem lies in your inexperience and poor technique. Henri Cartier-Bresson is one of the last century's greatest photographers. He shot almost all of his work with a rangefinder and a 50mm prime lens. I can only imagine him laughing in his grave at a debate between a D90 and D7000.
