I have not done Motion Capture with a Motion Capture system (harness, rig, etc.), -but I agree that would be very cool.
Instead, I use Motion Capture files. There are a lot of Motion Capture Library's on the net (.bip, .bvh, etc.). I have worked with some studios, -where they were doing Motion Capture, & my job was to take the motion capture data and turn it into an animation that looked good / would work well for 3ds Max .