Brian,
I have an 800AMP Odyssey battery in my car. IMHO, it's OK, but not great. If my engine doesn't fire(all in the past, I hope!)after a few good cranks(6 attempts or so), the battery needs a rest. It also has a hard time with "hot starts". It would be a tough call, using one on a high compression engine(800AMP).
Odyssey does offer plenty of higher AMP batteries than mine, which might be a whole different ballgame. They do get larger as amperage increases, but are still small in comparison to typical car batteries.
The size is great though(800AMP)! You could fit one just about anywhere. /ubbthreads/images/graemlins/cool.gif
Bill