What are the advantages of each?

I'm sort of a newb in the SLR realm, but can get a great deal on an EOS for just a little more than the XTi. With the double rebates, prices are close.

 

For a beginner, most of the differences won't mean much, but there are a few differences:

30D advantages:
Magnesium body
Larger grip
Pentaprisim viewfinder
Dual display
5FPS continuous drive
RGB histogram
ISO3200
ISO selectable in 1/3 stop increments
1/8000 max shutter speed
Rear dial for selecting aperture and moving through menus
Spot metering
Larger buffer for burst images
1/250 flash sync

XTi advantages:
10MP
Anti-Dust technology for keeping the sensor clean

 

We need a photo nerd smiley so bad.

Dan, what exactly is a dual display?

 

I'm sure I'm missing a few differences too.

The XTi uses the main LCD panel for both reviewing photos and for adjusting camera settings. The 30D has a separate display at the top to show the settings. For what it's worth, I don't think it's a big deal to have two displays.

 

I knew i should have opened the box when I had that 30D.

 

If money is not an issue, get the 30D. I checked one out in the store the other day, and it's very nice, with some good upgrades over the 20D. Very solidly built, and the shutter is substantially quieter than the 20D, one of my few beefs with that otherwise excellent camera.