I remember reading about that suit when I read the book (quite a while back) and thinking that the mechanism he described for moving the thing was quite cool.

Basically, he described a purely reactive system. The suit has some kind of pressure sensitive mesh/grid on the inside and constantly moves to try and stay at a neutral position relative to the occupant. (Example: you move your arm and your arm comes into contact with the inside of the suit arm. The suit moves the arm along the indicated vector until YOUR arm is no longer in contact with the suit.)

At the time I thought that this was pretty darn cool because it basically eliminates the need for a lot of complex control systems stuff in the armor. (although you would probably still need some kind of snubbing/damping or something) The human in the loop is still the primary control system/feeback integrator. You no longer REQUIRE gyros, balance control algorithms, etc. Basically you end up with a situation analogous to a hydraulically assisted flight control system versus a true fly by wire fight control system.

Granted, if you add all of that extra cool stuff you get a much more versatile device (like the one that John Ringo describes in several of his books, but I think it would be a lot easier to actually BUILD one in the manner Heinlein describes.

Wow, this has gotten to be quite a bit longer than I had intended ...