I've played enough of Overlord now to get a proper feel for the game (one of the seven bosses dead, three of the four minion colours collected). I am continuing to like it.
The PC control system works pretty well. The console version of the game uses an analogue stick to let you tell your minions where to go, on the occasions when you're not just saying "go in the direction I'm pointing", but need to steer them around the map. The PC version lets you do this by holding both mouse buttons and moving the mouse. This usually does not result in half of your minions drowning.
The different flavours of minion are also pretty easy to manage, because the game deliberately limits you to ordering one type around at a time, or telling them all to move at once. I presume they were tempted to include some kind of RTS-type grouping so you could order two or three flavours around in a group; I'm glad they didn't, if only because that would have further tempted them to make fights you could only win by doing that.
The level design is also good. The levels so far look like the kind of "natural layout" game levels in which you're forever wandering around places you've already been trying to figure out where the hell you need to go next, but they are not in fact that kind of level. Which is good, because there's no map display.
The level structure - move this to access that, get a shortcut back to the start when you get to the end, all that stuff - is also competently done.
I've seen a couple of bugs - the game locked up once, and there's other occasional oddness like minions that're carrying something getting stuck on an obstacle even after you've removed it. The bugs are easy to work around, though.
Back in the real world, I keep feeling the urge to order our cats to charge out, kill something, and bring back treasure.
The first part's probably quite doable, but the cats unfortunately do not share my opinions regarding what constitutes "treasure".