Sony dSLR Alpha A100 Reviews and Discussion vs Nikon D80 and Canon 400D
Personally I think the Alpha can’t fight, the only advantage it has is the in-body anti-shake system which frankly isn’t as effective as having it in the lens.

Image from dpreview.com
Having IS/VR in the lens means you can see the effects through the viewfinder and it’s more accurate as it’s tailed to the lens (each one having different focal lenghts, different aperture and different setups with more/less blades and elements).
Having tried the Alpha out the picture quality is ‘ok’ for an SLR type cam, but its not very exciting, the latitude or dynamic range doesn’t seem very great and the controls aren’t super accessible.
I’d go for the Canon 400D or the Nikon D80 everytime, if you have the budget of course get the D80 as it’s the superior cam but does cost more.
Also remember when you are buying a camera you are buying into a system, the bodies will come and go, what you will spend money on is accessories and lenses.
Sony lenses are expensive and hard to find, the second hand market is next to zero and finding anything for Konica-Minolta mount in Asia is hard.
KM was pretty popular back in Europe but it’s not here in Asia.
Anyway here is some info if you are considering getting a mid/entry level dSLR and specifically the Sony Alpha A100.
Reviews
DPReview Extensive Sony Alpha A100 Review
DCRP Review: Sony Alpha DSLR-A100
Imaging Resource: Sony Alpha A100
Comparisons
EOS 400D / XTi vs Nikon D80 vs Sony A100 - Camera Labs
Sony Alpha A100 Compared to the Nikon D80 and Canon EOS Digital Rebel XTi / 400D Digital SLR’s
