I bought the beta yesterday and only played a couple of hours co-op with a friend on the Headhunters mission. I have to say my 2 biggest issues with Arma have been resolved. Shooting is much smoother than in the past. That "clunkiness" I always felt with Arma has disappeared. Second, the inventory system is improved imo. I was able to easily figure out how to drag and drop inventory and understand what I had equipped. It no longer requires an Arma Inventory Masters Degree to figure it out :D But in defense of Arma 2 I never played continually enough to where it became second nature.
I am liking the new movements of the characters, the graphics are great, and I am just excited to explore more. There is that "feeling" that Arma gives you that no other video game can compete with and now it's even better. I understand people wanting the campaign right away and more variety of vehicle models, etc., but just seeing all the user created content already in the Steam Workshop is amazing. There is more than enough to keep myself and my few friends occupied for awhile already. I would rather have my content served this way instead of having it already created with no ability to add to it, bundled up and split into quarterly releases, that makes me pay double for the game.........because I have done that already.
Excited for more!