Sorry, didn't see this til now. Sorry but I'm going to be long winded now

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Wow, where do I start?
I had the Canon D300 (Digital Rebel) for the 30 day trial period Sears was offering. If you're going to be using JPEG only, then I'd say save the money and get that camera.
It has these advantages over the 10D:
1) Lighter (don't confuse the polymer body as being flimsy as it's very stiff. Stiffer in fact over the old D30-D60 series cameras)
2) A bit better low light sensitivity making for a faster focus lock-on. Will focus down to 0.5 EV where the 10D's lower limit is 2.0 EV. Keep in mind, using a flash unit with its infrared focus assist, will eliminate any DRebel advantage. They all seem to focus at the same speed down to complete darkness.
3) The price!!!
The advantages of the 10D:
1) AI Servo (continuous focus mode) on advanced settings. The DRebel only allows it on two Basic modes: Full Auto and Sports mode. If you want to shoot RAW files and you want AI Servo, you need to get the 10D. Canon dumbed down the firmware to not allow some features of the 10D. When you start going to 16 x 20" Pics and larger, RAW files are the way to go. At 13 X 19" and smaller, hard to tell the difference between JPEG and RAW.
2) Can shoot 3 fps for up to 9 frames as opposed to the DRebel's 2.5 fps for 4 frames. If shooting RAW files, this is a big limitation as it takes a while for the buffer to clear. I like to shoot RAW + large JPEG which the 10D allows.
3) Adjustable white balance in degrees Kelvin Adjustable @100.
I needed to switch to the 10D because I like to shoot RAW files so reasons 1 and 2 above were the main reasons for the switch.
I am completely sold on the 550EX so far. I have it set on the ETTL mode and it has been working wonderfully for me. I have my 10D set on Manual usually so all I need to do is take a couple of test shots, check the histogram info and make my shutter speed and/or apeture adjustments.
There is another "must have" item to have if you're shooting indoors w/external flash:
Tiffen's StroboFlip VH 2000 StroboFrame (you'll need to get Canon's #CZ6-2359 Off-Camera Shoe Cord 2).
When shooting indoors, particularly individuals, I favor vertical framing. The Stroboflip allows a fast/easy positioning that keeps the slash unit upright whether you choose to shoot a horizontal or vertical framed shot.
Worth its weight in gold.
If you are going to be favoring 13 x 19" or lower prints (even 16 x 20" turn out okay) then JPEG is the way to go. If the 2.5 fps @ 4 frames is not a bad limit for you, by all means I definitely recommend the DRebel. Awesome camera for the money. Get the 550 EX no matter which camera you decide on. Its just a flash unit not to worry about as it's that good. The people having problems with exposure issues just aren't reading the user's manuals of both the flash unit and the camera IMHO.
Althought the 18-55mm lens that comes in the DRebel kit is a good one for the money, I still don't like it. Get the body only if it saves you that hundred $ and spend it on the 17-40mm F/4.0 L USM. That lens "is all that and a bag of chips" heh. It is THAT GOOD. In fact that lens should arrive today as that will suppliment my 70-200mm f/2.8 L USM. My next lens purchase (which is a ways away) will most likely be Sigma's 120-300mm F/2.8 along with their 1.4 TC.
All in all, it most depends on what type of photography you'll be taking.
Canon's next camera I can only guess. It looks like the 1D is being phased out so I'm expecting something like this:
Canon 2D 6-10 MP @ 10-15 fps for 20-30 frames. Wireless file transfer capability. Probably priced in the $2500-3000. range. It will have even faster focusing than the 1D. Maybe based on a CMOS unlike the CCD of the 1D.
I'll try to see about uploading some images, but it'll have to wait for now.
Hope I've answered your questions to your satisfaction. Ask more if I haven't.
Regards.