Pauline and I were using a Canon Rebel XTi with a Tamron 18-270 lens and we were taking some very good pictures with the Camera/Lens we had. However, there were many folks along on the Tours that had Canon D50's with really good Canon Glass, that were taking Spectacular Photos. And there were a number of others, that were shooting with a Nikon D90, and they were taking Spectacular Photos as well. At the end of each days tour, several of our tour friends were downloading to our laptops and would make comparisons.
Although I like the Rebel XTi.........Like you, I am giving some consideration to making a change. And the Nikon D90 is at the very top of my list. Even though the camera has been out for some time now (think two years), it has really good reviews.
However, one begins to wonder if Nikon is getting ready to release a newer D90???? Don't know the answer to that question!
Picture of Mama Grizzly below, is with the Rebel XTi and Tamron lens.
Joe