Kind of like the more difficult scenarios of the various HoMMs. Not impossible, though. Several times, when I was tearing my hair in frustration and swearing I couldn't possibly continue, I'd try a new strategy and succeed (at least for awhile.) Actually, the most frustrating thing about the game is the camera angle. You adjust it (full 360 degrees) with the right mouse button, but it seems to have a mind of its own. Maybe I'm unconsciously pressing on the right button, but all of a sudden the view will shift from first-person to top-down view. I'm gradually getting used to it, though, so the view doesn't waver all over like it did at first.
I've been playing it since Christmas Day, and am slowly learning the ins and outs of the game. It IS addictive!
BTW, my version is DVD-ROM, not CD-ROM. I don't know whether it comes both ways or not.