Well, I started out playing Sisters of Battle but most of the people at my local GW play Imperial armies (Space Marines, Space Marines and more Space Marines, with some Space Marines for variance) so now I'm using my Iron Warriors.
Lost one (last week), drew one (3-3) and won one (4-2) today. The scenario was quite good for my army; I teleported in two units of Terminators and a Terminator Lord 5" from the Exit Zone and 9" away from the enemy's Hellblasters (in both games!) and blew away most of the unit before walking off the board next turn for 3 VP. Meanwhile my two squads of Iron Warriors and Sorceror were moving/advancing/warptime-move/advance down the board. First game they got stopped by an Ironclad, second game the two units of Iron Warriors died to a man but allowed the Sorceror to get off the board giving me the victory.
I like the special Stratagem cards you get for free and I like the scenarios, too.