Covers are actually pretty interesting and I hope Greg expands on them. Any metal plate produced in the plate bender can be used by right clicking it onto the machine while holding it. Either the railcraft or gregtech crowbar can pry them back off. The heat vents are probably the most interesting cover so far, given that they can increase the energy efficiency of the machine (3% is a big deal when you start adding a bunch of overclockers). Regular metal plates will block connections. Conveyors provide the same item output functionality to ic2 machines that is found in most gregtech machines via the -> button. I was really hoping the pump cover would let me pump liquids in or out for/from cell recipes, but that doesn't seem to be the case. There's also a number of redstone covers.