First off I'm not the greatest RTS game player around. In fact of all the genre's it's my least favorite next to Platformers.
That being said I'm a LONG time Warhammer 40K player (2nd Edition baby!) and I've been a Tyranid player since forever. So needless to say I HAD to play this game.
First off let's get this out of the way: The game looks great! So great in fact it's the first game I've had to turn down the graphics on my Macbook Pro to play properly.
Secondly the Campaign is (so far), Space Marines only. As a Tyranid player you can imagine my disappointment to discover that I can only play as SMURFs. Though the game does a good job of making them fun. Tyranids are multiplayer only, but you can always skirmish to play as them and let me tell you, nothing is quite as fun as watching a swarm of bugs roll right over those annoying space elves, I mean Eldar, with all the awesome kill animations.
In skirmish mode the game plays very much like the previous Dawn of War Series, but with better hero units.
The campaign is where this game shines in my opinion because it gives the game a bit of a Strategy RPG element to it. A kind of Real Time Xcom if it were. The constant leveling of your squad leaders also gives the game a bit more "Warhammer 40K" feel to it from the tabletop. Wargear, talents, and other bonuses are very nice.
All in all it's a great game but not perfect since it IS an RTS and I have inherent problems with the Genre.