I wouldn't have the Sony if they gave it to me, just because of the
way they treated those of us who had Minolta 7d's that died. You
basically get the same warranty service as someone who has a dead
walkman-minimal. I did play with the Sony Alpha, and didn't like
the feel, too plasticky.
However, I DID want the in camera stabilization, so I went with a
Pentax K100d, and wouldn't trade it for anything. Nice feel, nice
controls, and great pictures. Add that to compatibility with darn
near any Pentax lens ever made, and I'm happy.
Suggestion....I know you've done a lot of "auto" shooting, so don't
stop that, but add a step to it. When you take a shot, make the
first one in "auto" then go to full manual, set the same
shutter/ISO/aperture the camera chose, then try changing one or
more of those and shooting the same shot again to see how it
affects your images.
Also, get a Magic Lantern guide for whichever DSLR you get-great
book to have.
And I would go Sony for the same reason... How they have handeled Warranty service of abandonded cameras.
Konica Minolta walked away from the 7D and Sony after a bit of a rough change over.. has been repairing known issues out of warranty and if they don't have the parts buying back the 7Ds often for more than their market value. on websites like Walmart that were selling the last ones.. And yet Sony never sold one of those cameras nor made a dime off them. And probably had to sell five A100 to pay for each 7D buyback.
Lots of misplaced anger over KM walking out has been lumped on Sony.
The A100 has been way more reliable than either the 5D or 7D with their known issues like first black frame etc. I have seen very few "sent my A100 in for repair posts"
You have lots of great lenses to choose from both new and old and ALL of them unlike Canon or Nikon have stabilization in them to help with low light shots.
The Sony also includes features not on the Nikon or Canon.
Spot metering.. not on the Rebel
Auto braking of both exposure and WB (never use Wb bracketing) not on the D40
Compatibility with all the Minolta Auto focus lenses.. D40 requires the more expensive AF-S lenses
Wireless flash triggering not on either the Canon Rebels or the D40..
And of course the body is stabilized so you can choose from more than the select chosen lenses. There are some great bargains from companies like Sigma and Tamron not stabilized on the Nikon or Canon but stabilized on the Sony.
INMO the Canon and Nikon's systems really start with the 30D and D80... not the D40 and Rebel...
The A100 has a magnesium frame that ties key points like the base tripod mount and the lens mount. So people mistake light weight for poorly built, which it is not.
The Sony is based on the KM5D which I shoot and find a total joy to work with...
don't let an abandoned KM user talk you out of a great starter camera.. with lots of room to grow with features other reserve for their $1000 + cameras...
http://www.ppmag.com/reviews/200705_sonya100.pdf
This is a Boston Shot taken at 90mm at 1/13 second hand held with a well reviewed close-out lens (MSRP $499) that I got for $120 last year. Can't do that on a Nikon or Canon as the IS/VR lenses always add $100 to $200 to the price... (and before the replies begin.. no I didn't want to carry a tripod with me all day for a few evening shots.) And the A100 stabilization is suppose to be just a bit better than what is on my camera.
I like the Canon system but wouldn't buy less than the 30D..personal preference for build and feature set.
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Ken - KM 5D
http://www.cascadephotoworks.com 
