But it's the same system
I was about to say the same thing.
There are definitely more special rules to keep track of in Deathwatch just due to the sheer number of abilities Astartes have and how deadly their enemies need to be in order for them to be challenging, but the core mechanics are essentially identical with a few exceptions (like psychic powers).
Either way, I can't wait to get my mitts on this book. I just recently got a copy of Daemon Hunter and I'm rather pleased, so let's hope FFG can do the line justice with its latest addition.