I had a bad experience where I left the IS on my 24-105 f/4 L two years ago. Of course, I did a thread on the topic. I was trying to photograph a favorite waterfall that was completely iced over. Almost all my shots taken from the tripod were ruined where my hand held shots were fine. As I mention in the thread, I contacted Canon who thought the low contrast ice and snow played havoc with the feed back loop you mention on the 24-105 L. But, I was able to less consistently observe an issue at home with an ISO 12233 chart (high contrast). My conclusion was that the 24-105 L's tripod detection system is just not as good as some other lenses I was used too (15-85, etc).

All that said, I do my best to remember to turn the IS off when on a tripod. I don't always, and have not observed a problem other than that time with the ice falls. But that is the easy solution is to turn the IS off.

But, echoing from above, if you want a truly dedicated macro lens that will be almost always shot from a tripod, you wouldn't need IS. But, for walking around your yard or a park, doing portraits, etc. IS is great.

Last comment, but for the few times I have tried "true macro" shots, I've thought 100 mm was a little short. You can only get so close. I can see the 180 mm Macro or the MP-E 65 being better if you want a true dedicated macro lens.