I have warfighter, it's a good system - especially if you like the WW2 theme. I've only played it a couple of times though (because I have more money than time lately...).
I don't know if you've played any DVG games but this one has a similar flow than his others (with different mechanics). You pick your mission, pick your soldiers and gear them up.
You then start the mission and draw a hand. The missions are timed so you're often times under the gun to move but the terrain is placed from your hand and it's possible not to draw a terrain card or to draw a very unfavorable one. The terrain dictates how hard it is for your soldiers to move to it (movement points are different for each soldier and you can supplement their movement with card discards or playing certain cards). The terrain also dictates how many initial enemies might come and reinforcements that enter on a per turn basis (this is also randomized via card draws, the terrain simply says which draws will be valid which changes the odds).
You work your way through the map and try to get to the objective hex and complete whatever the objective is (it might be to destroy a bunker or to hold the terrain for x turns, etc..).
Games take about an hour once you know what you're doing. I'd say if this interests you at all to go for it. As far as which expansion to get - personally I got none. I don't plan on playing this more than occasionally so the base game has more than enough variety for now and DVG games tend to stay in stock so I don't have fear of never getting any expansions.
Also - there's a modern version (think of a seal team or something like that) and he's going to have a kickstarter for a fantasy version. If either one of those themes interest you I'd get one of those instead. It's really the same game but different themes - no need to own all 3 IMO unless you are going to play them a lot.
edit: Oh a bit about your hand. The cards are pretty varied and have a lot of interesting actions you can take. You also have opportunity to discard your hand entirely if you don't like it (at a cost). Cards are generally played at any time it's your turn (some can be played on the AI turn IIRC).
The AI movement / attack is pretty straightforward. There's some terms you have to get used to but it's not a difficult game to learn to the point where you're mostly having fun and not consulting the rulebook every action. It's deep enough IMO - I wouldn't want it any more complicated. I wanted a quick fun to play game when I bought it.
Component quality is also very good - mounted map, nice counters. Good clear cards. Manual seems well done.