I just bought the base game + marines bundle and have been really enjoying it, this is the first serious wargame I've played and learning it has been a ton of fun. I only started learning about tactics recently and most of what I know is very basic small unit tactics, so learning about combined arms through the scenarios in the game has been really engaging and difficult, but very fun. I was curious if there are any chatrooms that can be used to talk about Combat Mission or ask for advice, a lot of times it will take me playing a scenario several times before I figure out a viable and realistic course of action for it and being able to ask for advice could be very helpful.
I'm partway through the Marines campaign right now and feel like it's a fair bit more difficult than the TF Thunder campaign, I had a lot of trouble on a scenario where you have to use a reinforced rifle platoon to take a mountain pass from a company of airborne infantry. I'm also a bit unsure how to use the CAAT teams without getting them killed immediately. It's very interesting to see their equipment in action though since I'm interested in working in the Marine Corps when I'm older, I never knew their squads had so much firepower! Once I play my fill of Shock Force I'm planning to buy Black Sea since it looks really interesting, I'll probably pick up Afghanistan at some point also.