I just finished up the single player campaign last night on Hard difficulty - a friend tells me Normal difficulty is far too easy. In retrospect I should have given 'brutal' a try, and I don't consider myself terribly skilled at RTS games. Ultimately the downfall of the AI is consistently passing through/attacking the same 2-3 choke points. It was a little on the short side, but I thought the levels were nicely designed and do a good job of letting you get familiar with the various units.
The multiplayer from all I've heard is very balanced, despite the three sides playing very differently. I have the hardest time playing the GLA properly - it requires a lot of micromanagement and sneaky tactics, not my usual style of RTS play. With any of the sides it seems like you do better with mixed units and it's not just a matter of massing up a ton of the 'best' unit.
If they come out with an expansion that has a significant sized additional single-player campaign, I would get it without hesitation. I got a respectable number of hours out of the main campaign, and I'll probably do a little skirmishing against the AI on the multiplayer maps and then have a few multiplayer games with RL friends. The editor looks usable too.
I'll probably slow down the speed on the skirmish vs. AI games (there's no speed option for the campaign, which I find wierd), but I'm the type of player who would rather play a turn based game than this new fangled real time stuff.
