Well......good question. First off, I'd agree with what the first respondent said - that the only BIG improvement you can make would be to go full-frame, but that was not financially possible for me. I'm a former Canon shooter, and variously used the 450d, 50d & 550d. I was pretty happy with the 450d as a camera for hiking, used with good lenses (I used mostly the f/4 L zooms - 17-40, 24-105, 70-200). I quit shooting altogether for awhile and sold all my gear. When I got back into it recently, I got a Nikon D7000. The reason I did so was the greater dynamic range and better shadow noise characteristics of the sensor. As a landscape shooter, DR was always a challenge - you know, you can't burn out the highlights on the white water, then the rocks go black, etc, etc...... And the D7000 is definitely better in that regard than any Canons I had. But it's not worlds different - don't think I'd have swtiched had I kept shooting all along. I also liked the color & contrast of the L lenses - not that you can't get that from Nikon lenses, I just don't know which ones they are yet. I'd also say that the handling of my Canons was far better than the D7000. This post would be too long if I went into the details, but accessibility of important functions was far better on the 50d and okay even on the 450d. The implementation of live view on the D7000 is almost useless (good only for framing & manual focus), whereas Canon's live view served for framing, focusing, judging exposure and mirror lockup (with electronic first curtain shutter to boot). On the other hand the viewfinder on the D7000 is much, much better than any crop frame Canon. (This wouldn't apply to D3200, D5100, etc.) So in summary, if you're a DR-challenged shooter, then the switch you're contemplating might make a significant difference in your final IQ. If that's not been a problem for you, then it won't.
