Btw, I had to rig something with Armature modifier and vertex groups in 2.55 and I must say that it has really working nicely now.

You just define vertex groups with the same names as your bones and voila, Armature modifier begins to work.

It might be one way to solve mechanical movement, I used Weight value 1.0 with all vertexes which is, well, hard surface stuff.

Nice thing, which I have not tested, but I assume that should work, is that you can use one Armature skeleton with several models/meshes, so if you develop poses for one mesh, they might work with others... Of course you probably need to "fit" the Armature with each model.

edit: typos