Your summary? I would say that Deathwatch has changed the way marines are being looked at - for the better. It also has further cemented a more movie marine interpretation of Space Marines. Furthermore we now have mortal and Astartes grade weaponry which is new and not to everyone's liking. FFG isn't blame here though but it has to be placed at BI's feet for underpowering DH's bolt weaponry. Personally I think it makes sense if marine weapons have a bit more buck than what a mortal can fire and that most bolt weapons are cheap knock-offs. But the bolt weapons of Inquisitors and SoBs should have some bang.
That much debated issue aside, we have been getting a nice, detailed look at specialties and chapters. RoBs has done a good, if partially inadequate (because too brief), job here.
More things can be said but overall I think the biggest impact of this game on the 40K world is the change in perception of marines. To a lot of gamers marines were they-are-all-the-same guys before DW. I think that has changed.
And the concept of playing marines works. Even if I'd like to see more about the sociology of a Deathwatch Space Marine's life beyond endless training and meditation. What are the rituals on Erioch (upon initiation/death/etc)? (I am waiting for an Erioch sourcebook anyway.) Do they get on patrol? Do they have standing contacts on various planets? How does interaction with the present Inquisitors work in detail?
Alex