Well, my only drills are a cordless and a wired hammer drill. The hammer drill is way heavier than the cordless (just a 9.6v Black and Decker). I don't think I've ever even tried to use the drill guide with the cordless because it's really too weak to handle serious work, and for work that isn't serious I don't need the kind of precision that would call for a drill guide.
The thing is really something to set up, though. It has a couple of set screws with points on them that you screw down and they press into the wood, giving the thing some traction. Obviously this isn't an option on a piece that can't be marred. But you have to be careful, because it's very likely that the last time you used it you just picked it up, unhooked the drill and put it away, so the set screws are still protruding down past the base. Set it down on something without thinking and you just marred your surface.
Then just getting the thing all lined up is very difficult. Once you have it, because it's so top-heavy and unwieldy, it's easy for it to move out of place (which defeats the whole purpose of the thing). Controlling depth is nice, but just get those little drill stops you screw onto the bit for that. They work well enough and are 1000x easier to use.