Canon EOS Digital Rebel XTi (400D) 10mp comparison with Rebel (300D) 6mp

For the last 2 years, I have put my Digital Rebel 6mp through it's paces. As a "semi-pro" photographer, I've experimented with a wide range of conditions (light, temperatures, distance) and have been quite happy with my Rebel. It's given me four photos that have graced the cover of our local 'tourist' publication.
But time marches on, and now the greater megapixels are available at a reasonable price. To make the jump or not? For me, the newer 10mp Rebel would give me increased options and flexibility in my photo taking. I've already invested in some lenses for my Rebel, and my husband would like to keep the 'old' Rebel for his use.
The XTi model accepts the current Canon EF mount lenses, same as the old Digital Rebel (and many other recent Canon SLRs). A quick search of eBay provided some background - prices from the $600s (body only) to $1,000s (various kits or combinations), based on the kit, camera body color, and optional equipment. After much searching and consideration, I went with B&H Photo in New York (their online store is excellent, as is their easy check-out, great prices, and shipping speed) and got the basic kit: Digital Rebel XTi body (black - my old model is silver), 18-55mm Canon lens, and battery charger (also includes battery pack, interface cable, video cable, and wide strap).
The new Rebel XTI is smaller, and much lighter, than the old model. I was shocked at the difference in them! For me, the newer one is delightful to carry and use. I can reach the manual setting buttons easier. The preview window on the back is larger, with easier to read print for the optional settings. The performance is faster, and quieter. Of course, with the higher megapixels the images appear sharper, especially for larger image use. The shutter makes more of a soft "whirr" sound, less of a "click" than the old Rebel. Many animals and birds I photograph hear it, but often they listen to try to determine what the noise is rather than bolt away. The Canon EF lenses are interchangeable - I use the Canon 18-55mm that came with the kit (each of my Rebels has one), and the Canon 75-300mm telephoto AF lens, each with the same great results. The new Rebel XTi also has a few more setting modes and manual options than the older model, further expanding its flexibility.
I tried my Phoenix Gold 100-400mm AF lens, and it works great. I also tried a Phoenix 2x teleconverter with my Canon 75-300mm lens and using it with the Phoenix Gold lens, but in the distant ranges of focus, it fails to autofocus. It worked fine in the closer ranges. I've got to have the autofocus - can't trust these eyes! (I may have a defective teleconverter!)
The Kit includes software that is upgrade of my two year old program (Zoom browser EX), and includes a decent photo editor. The photo editor has one feature I adore - it can be set to make the same adjustments on a whole group of photos at the same time. Super for the occasions when I want to change a number of photos to 72dpi.
Now, the (small) downside. The new Rebel XTi does NOT use the same battery pack, or battery charger, as the older camera. I'm glad I got the Kit! The interface cable appears different, also. The camera, and many of it's package deals, do NOT include a CompactFlash memory card, which must be purchased separately, and the camera requires one to operate.
For me, the new Rebel XTi is lighter, easier and more powerful than it's predecessors. Just be sure to buy CompactFlash memory cards when you get your camera: it does not come with any. I strongly suggest at least 1 gigabyte cards, which hold about 180 images in large format jpeg mode. Each brand has a selection of write speeds, storage capacity and prices, but that's a whole 'nother epinion!