The Competitive Set
($1,100, street, with 18-55mm f/3.5-5.6G ED AF-S DX Zoom-Nikkor)
The D80 costs $200 more than the Rebel with the equivalent lens, but dealers can't keep them in stock. Well-deserved popularity, as the D80 produces Excellent resolution, even at ISO 3200 (which the Rebel doesn't even go up to), and its noise control leads the league.
The Nikon applies noise reduction in a distinct chunk around ISO 800, resulting in lower noise than at ISO 400 -- along with a noticeable dip in resolution. So by ISO 1600, the Rebel XTi, while noisier, delivers somewhat higher average resolution than the D80 -- about 1,985 lines versus about 1,825. It's not a big difference, but there.
The D80's wireless flash triggering has it all over the Rebel, and it has a selection of useful in-camera fixes. And we think it's a little better-built. But the Reb can meet or exceed the resolution of the D80 at higher ISOs (at the expense of more noise), and can autofocus faster than the already speedy D80.
Sony Alpha 100
($850, street, with 18-70mm f3.5-5.6 Sony DT Zoom)
The Alpha 100 is one great deal, given that its CCD-based Super SteadyShot works with any lens, while you have to buy individual lenses to get image stabilization with the Rebel. It has terrific on-the-fly dynamic range fixes, autofocuses faster at lower light levels, and has built-in wireless TTL flash triggering. But the Rebel has significantly better image quality (both resolution and noise suppression), more sensitive AF, and is backed up by that huge Canon lens catalog.
Pentax K10D & Samsung GX-10
($1,000, estimated street, with 18-55mm f/3.5-5.6 AL Pentax SMCP-DA Zoom or, on the Samsung, Schneider D-Xenon 18-55mm f/3.5-5.6 zoom)
The Pentax/Samsung clones have much to recommend them: They are better sealed than the Rebel, and, like the Sony, have sensor-based anti-shake. They also can provide wireless TTL flash control with the built-in unit. But the Rebel's image quality and autofocusing have set the bar very high for these twins. We'll have a full test of the K10D and GX-10 shortly, so stay tuned.