Well its not that they don't do anything exactly, at least with the discharge and cloaking module which I tested in single player. Its that they don't actually install into the armor in multiplayer. Once a module is properly installed it actually says what it has installed in it in the little description.
Oh I also noticed in the creative mode tab, the mod is organized neatly in single player but in multiplayer things are a bit out of order. I'm not sure if that matters.
I suppose I should add I tried on ic2 version 632 then 633.