Played a game of this last weekend. Man was it a blast. We just played through the scenario from the Game Masters Kit to break in the system, and had a ton of fun. Our GM had run both Dark Heresy and Rogue Trader before, but none of us were really prepared for how powerful the Deathwatch marines could be, even at the start. We destroyed and entire Tau hunter cadre in a firefight fairly quickly, including a Crisis Suit and 3 Stealth Suits, and took almost no damage in return.