This is the only RTS I've ever played that didn't make me feel like an idiot (I love Starcraft and C&C clones to death, but they kick my a**). I actually found the difficulty to be a bit on the low end on average, although certain levels are significantly harder than those around them, the difficulty can be inconsistent from level-to-level.
OW is certainly not without it's flaws. I've mentioned the difficulty, this is because the strategy can be fairly simplistic (climb the tech tree until you can build an unlimited supply of automatic vehicles). Actually, the early game can be harder because the tech-tree limitations make brute force options more difficult. But this is a big part of what makes OW fun, and it's most enjoyable if you approach it more like an RPG than a typical RTS. The script is awkward, but the story it tells is high quality, and it's hard not to fall in love with the characters despite the way you'll cringe at their lines. Making it through to the end with all of them alive can be a challenge, but I always have difficulty letting any of them pass, even though it can mean losing the "no loading" medal after a mission. The focus is always on your team: when a character is killed, his icon is not removed from your menu tray. Instead, his portrait is grayed out, and you have to click a "bury" command to completely remove him from the tray. A minor detail, but a surprisingly powerful one. It's hard to press that button, even for a lowly apeman you've recruited (R.I.P. Bongo).
I suppose that's all I have to say. Five Stars. Not because the technical aspects are all that outstanding, and not because it's perfect. But it's an engaging game, and one I'd recommend to absolutely anyone simply for the story. Well worth playing. I got it for the original $20; $6 is a definite bargain.