I got a chance to play around with the Canon 100mm f/2.8 macro lens recently, and came to the realization that macro photography is tougher than it looks. With no depth of field at such close distances, it's imperative that you stop down...which in turn slows your shutter speed. A tripod is needed at the very least, and manual focus is advisable. Macro shooters know this, of course, but I'm usually late to any party.
It was the first time I've used "live view" on the 40D. Other than macro, I can't imagine using it again, really. Maybe for a portrait. To me it's a vestigial feature meant for marketing bullet points. Shooting macro on a tripod, however, it did come in handy.