new to posting here.. didnt actually realize there was a photography section on mac rumors... i can offer advice here though... with lightroom, it doesnt directly allow it, but you can do it... i use nikon, so I cant directly tell you what to do.. however, I do believe that canon has software for tethering as well... what I do.. is i run my nikon camera control pro (which is the tethering application that allows me to shoot pics directly to my computer... i just run it in the background, cause I actually use the camera to edit settings and such... in the forground though, I run Lightroom 2.. in LR2 ther is a "auto import" feature... (find it under file) it automatically scans whatever file you pick, and whenever there are new photos in that file, they are automatically imported to LR.. so I set up LR to automatically import from whatever file my nikon camera control automatically downloads to.. it takes about 2 seconds for the photo to appear in LR, but it works great.
hope that helps