I've been playing OFP and Arma 1 and 2 for over 10 years now and I've never had a problem with the controls AFTER I tweaked them.
There are some things that take getting used to, like fixed animations that take X amount of time, but it's not difficult at all.
The main weakness is the missions BIS made for them. Some are good, some are lousy, but there is a never-ending fountain of new missions using just the stock units, not to mention the tons of mods. So forget the campaigns, you'll get stuck and frustrated and think "OMG this game is crap" when it's just the way they made those missions.
Zero out the aiming deadzone and head bob, keep smoothing at a minimum, and it works well. Also, there is some inertia in there because it's not at all realistic to swing your M249 around 180 degrees in under half a second just because you can in game X.