Yes, if you shoot off a tri or mono pod, you're better off turning off the IS. Some Canon bodies incorporate IS in the body... mostly you'll find the IS on the lens. I believe that Nikon does the same (but again, I'm a Canon shooter so I don't know for fact).
I've shot sports with IS mode 1 on. I felt like I was fighting the IS when I panned to track the action. There were some jumps and bumps during that battle.
These are some B-roll shots (the A roll belongs to the service I shot for).