The game is a really fun squad based tactical RTS. In the campaign you control a team of 4 squads which you select prior to each mission. Your units level up and there are random loot drops that you can equip on the hero that commands each unit. This customization is surprisingly deep and the loot you equip along with your choices in the skill trees will really influence how you tackle missions. There is no unit building in this mode, but the campaign is really well done and it includes linear campaign missions along with random missions for leveling up and gathering loot. There is also a 'strategic asset' mechanic where you have to seize structures on each planet that give you bonuses. You might have to defend these from attack in order to keep control of them. You can also play the campaign in co-op with a friend, which adds some additional fun to the game.
In the online versus modes the game is much different as you pick a hero and then have to build your own units. There isn't really any base building like in starcraft, but you do have to control energy and requisition points on the map in order to generate resources to build your army. Unless you are good at starcraft or other RTS games you will probably not have much fun with this part of the online as the die hards that still play are all very good and know all the nuances of the game.
The online mode that is the most fun is Last Stand mode. It is a co-op mode with 3 total players against waves of enemies. This mode is kind of like an RTS version of Gears 2 horde mode, if that makes sense to you. You level up your heroes based on how far you get into the 20 waves and you get loot and perks to customize your heroes further.
The game is a great value at the $29.99 steam bundle price, but it will go on sale pretty cheap from time to time so if you want it cheaper just wait until the big holiday sale in a couple months.
One last thing, the game does use Game for Windows Live so that does turn some people off, but it does support xbox live achievements and you can get 2000 total gamerscore, the only game to support that many points for one title.
