No one that jumps into Arma likes it at first for a few reasons:
The controls are complicated and clunky.
It plays very, very differently than the normal FPS. Heros and RAMBOs die, quickly and over and over. You need to think and play with others as a squad to succeed. Success often means just controlling an area, not killing everyone on the other side.
Since it's a realistic environment, it's takes a while to be able to hit anything accurately, especially at distance. You need to control your breathing and stance. No laser shots in the midst of the sprint here. Suppression also works and works well. Half the time you're shooting to suppress, not so much to hit anyone.
Big maps mean unlimited avenues of approach and retreat. Also, since there are effectively no walls, you can always get flanked. watch your back.
Big maps mean long range firefights. It's hard to see where the enemy are, where fire is coming from and who just pinged you.
There's no gamey BS, no leveling, no perks, no nothing.
I tried A2 after release for a couple of weeks and gave up in frustration, it was a buggy mess and I just sucked at it. I couldn't get the awesome scale of battles out of my head though and came back after @ 6 months (and a bunch of bug fixes) and once OA came out I was hooked. It still lacks in a lot of areas, but it provides an experience like no other. You can't compare HOS and A2, different philosophies and end results.
I hope BIS can improve A3 enough to make it more accessible to the hardcore gamer and less frustrating as well.