I played this a bunch on Steam some time ago. It's well-done; if you think it looks interesting to you, go for it.
Vythonaut: It looks quite nice, but the whole DLC / modular thing puts me off.
The DLC is mostly if you're playing multiplayer or if you're heavily into single-player skirmishes, and want more clans to experiment with. Honestly you're better off just buying the base game, and if you really like it, buy a few DLCs later. There aren't any game features locked behind DLC; the base game is complete with out them. I bought at least two of them, and they're fine but not necessary.
Nicole28: Is there a random map mode in singe-player, or is it campaign only?
It has random maps.
timppu: Argh! So is this one of those RTS games where you can't slow the game down yourself, or give orders in paused mode?
No, it's not like that. There's no real need to slow or pause the game since you only ever control a handful of units at a time. It's nothing like Age of Empires, Starcraft, etc. For all I know it may actually have pause, at least in single-player, but I can't remember since I never needed it.
Cavalary: First question is what are the "online features" mentioned (that Galaxy is required for). Just multiplayer or is it a game where the single player experience is hampered by being offline too? :/
It's only for multiplayer. Specifically there's both standard matches and co-op, though the co-op was added more recently and I haven't played it.
kai2: Played some skirmish on console and quite enjoyed it... but... it was pretty darn hard, even on normal difficulty. Didn't get to try story mode.
I can't imagine wanting to play this on a console, using a gamepad. I can see that it would be somewhat more feasible compared to a more typical RTS game, but still, it really kinda needs a mouse.