Canon 7D - One Shot/AI-Servo w. macro?

What do Canon 7D shooters find works best for them? One Shot AI or AI-Servo? I am shooting with single point focus and playing around with both modes with the 100mmL. I read someplace (and cant find it now of course) that the AI-Servo when used with lenses 2.8 or faster has more sensitivity and can track both X,Y but also Z movement... Seems like it could be very handy for underwater where we struggle with both moving subjects and moving water/surge.

Anyone with any experience testing this out?

i'm shooting with a 20d but have used single point focusing and AI servo on both the old 100 and now the 100IS. i have a 7D used mostly for wildlife and just purchased Art Morris's setup instructions. his instructions are directed toward bird photography, but are mostly applicable to anything that moves and were helpful to me as the manual is typically confusing. Art loves the 7D autofocus and i recently shot some terns in flight with better than usual hit -rate, under other circumstances i'm not sure i see that much difference - but also haven't entirely got the settings sorted out yet.

I used the servo setting with my 60mm macro in the red sea two weeks ago with no problems. I can't say I've played with it too much since the majority of my photo opportunities this Summer have been wide angle.