The expansion is cool so far.. I've only played through the Tiger Ace single player and it's super short (maybe 30 mins) but lots of fun.
They added a few new multiplayer maps, haven't really tried them yet so I can't comment but it's a nice addition.
I tried two of the new game modes, I don't really remember what they're called. One is pretty much DOTA and was lots of fun. The other one was still a little like DOTA but with tanks and control points, we tried it 1v1 and it didn't make alot of sense. I imagine if you were to get a 3v3 going in that mode it'd be alot better.
I also tried the 3v3 map, the Scheldt and they changed it around a bit. All the bridges in the map are now destroyable. I wonder what other maps were changed.
The added medal system is kind of cool, makes me want to play through more of the single player stuff.
So far so good though. I haven't had the chance to try the new units outside of a motorcycle replacement and the new tiger, they looks like just reskins. Time will tell how balance plays out or the new modes are, but so I'm liking it so far - worth the 30 bucks imo.