I've shot tethered to both an iBook and an iMac Intel with Lightroom of various revisions on it.
It works great, once you do something strange to get the canon software to recognize the camera.
Make sure you camera is in PC Connect mode, connect up the camera, then either review an image, or take a trash shot and review it. Launch the EOS Utility, and then when the warning that the camera is busy pops up, clear the image you're viewing and you're connected.
This only started with Leopard, it didn't do it on 10.4. I'm guessing there's a glitch that Canon hasn't fixed/doesn't want to fix.
Once that is done, you can shoot from the computer if your camera is on the tripod, or hand hold if you like. You'll need to get a long enough USB cable or you'll find yourself yanking it off the table if you're not careful if you're hand holding. It's just a standard USB to Mini-USB cable nothing special needed.
Only warnings I've found so far -
1) I shoot to both card/computer. However when card fills and you change it, it disconnects you from the computer too. So make sure you reconnect. I was doing an event where we were printing live as I shot and suddenly no more photos were in Lightroom and had to do a scramble import.
2) I rarely shoot tethered, and I like to hand hold as recently my subjects have been small kids. So a standard height on a tripod is pretty hard to do with varying ages of kids. So that cable can be a PITA, and finding a good long one is either ridiculously expensive locally or hit or miss on the web with cable quality.
For on demand printing I use a mitsubishi 9550 and usually print 5x7s. There was a deal last year on them and the rebate was five or six boxes of paper. Have yet had to buy paper for the thing now and its been over a year.
Hope that helps.