So far I've spent only about two hours trying it out, but I think I like it.
Initially I jumped into the deep end by selecting expert difficulty, which offers the most complex flight model, and tried out the MD500 (the lightest chopper) in free flight mode. It quickly became apparent how sensitive the controls are, and I found myself taking quite a firm grip on the joystick. I was using a Thrustmaster T-Flight HOTAS X (not my usual controller) with collective mapped to the throttle and anti-torque controls mapped to its paddle buttons. Raising and lowering the collective is accompanied by corresponding torque-induced yaw, which in this helo is quite noticeable, especially on this difficulty. I also noticed that I was having to fumble around with trim quite a lot. The default trim controls are right-ctrl and numeric keypad keys, which I found difficult to use as I had to take my hand from the collective. Eventually I found it easier to trim by mapping anti-torque trim to a couple of throttle-mounted buttons and the cyclic trim controls to the POV switch/coolie hat on the joystick, which made it seem less like I was constantly fighting for control. On trainee mode the torque-induced yaw is less noticeable and I found myself trimming the controls less frantically.
I found that keeping tabs on the instruments on expert difficulty kind of tricky. I have to use the mouse to move my head and zoom in on the instrument panel, but with head-tracking software this would probably be a bit easier. On novice and trainee difficulty settings you get handy HUD gauges for airspeed, altitude, VSI etc. and a velocity indicator, so you don't need to focus on the instrument panel. All the difficulty settings have features that can be customised, but on expert level some of these features cannot be selected, such as the aforementioned HUD gauges and indicators. I might try it with TrackIR if I can get it installed, but it will take some getting used to.
The helicopters have an auto-hover control that can be enabled by pressing the spacebar or using the mouse-activated menu. I think it might be a little too effective though, because it seemed to stabilize the helo with no extra input from myself after activating it whilst inverted and at other odd attitudes. Maybe real auto-hover/stabilization systems are that effective, I don't know. Another thing I noticed was that when I approached about 500 km/h in the MD500 (an excessive speed for this aircraft) the computer seemed to take over and initiate a sort of hammerhead stall maneuver. I think this happened in trainee and expert modes - I might experiment a bit more with this.
Progress so far with the career mode has been quite slow, I've only got as far as the first proper "mission", after which I realised I needed some training lessons. I think I also might switch to trainee mode for a while and later on switch back to expert. Another thing I've noticed is that the AI pilots seem to fly in a jerky manner, at least from what I've seen so far from sitting in the co-pilot's seat of the UH-1 as a passenger, but that's only a minor thing. It's a nice change to have a flight sim that's story driven, and the training lessons are kind of educational and don't bombard you with too much information all at once - you can pick and choose which aspects of the training you want to go through in any order.
Graphically the helicopters look really solid, whereas the ground texture resolution is kind of low. This was probably a necessary compromise. Still, it's fun buzzing the traffic and dodging trees when you're down low. I quite like the vibration and buffeting effects that you can see whilst changing attitude and maneuvering, it really adds to the atmosphere. Compared to helo flight in MS Flight Sim it makes it feel a bit more realistic, because it doesn't seem like you're in a static, rigid cockpit.
Whether it's a study sim or not I'm not qualified to say. I did notice an in-game loading screen with some text that said something like "Take On Helicopters is a game and was not developed... something something" - I didn't read it quickly enough to take it all in. The only other Bohemia Interactive title I've played is Operation Flashpoint: Cold War Crisis but given that there are similarities I think TOH would be quite accessible to ARMA players.
I think I'll need to play it a bit more before I make my mind up. What with Combat-Helo and Jet Thunder possibly making an appearance in the next few months I might put off making the decision for a while.