I'm going through the learning curve now with my new board, so I'll offer some observations. Hopefully, they will make sense, and maybe even help someone.
First, the OW is actually far easier to ride than I'd expected (at least on smooth surfaces - my only experience so far). I don't have any board sports background. Nevertheless, in an hour I was making controlled, tight doughnuts at low speeds, comfortable cruising faster, and carving much better than I'd ever have forecast. I'll credit part of my early success to buying a cheap skateboard and a balance board, but honestly I didn't practice with them all that diligently (and I find skateboarding to be more difficult because of the following). The rest of my success I'll attribute to having a motor (especially a self-balancing motor): Coordinated turns require balancing your lean angle with your velocity. If you lean too much for a given speed, you'll fall over. With the OW, you can fix that mid-turn by simply accelerating. Without getting off an a tangent, you do have some similar options on other types of boards, but those options are more limited than the instant velocity changes you have on tap with the OW. I'm finding learning to ride to be rather easier than it looks. Another suggestion I'd offer is to start out by practicing for a good while getting on and off in front of a rail to balance yourself, and then practicing riding forward and backward in a hall narrow enough to balance yourself against the walls. Very slow speeds are harder - practice those.
Graduating myself out of the house, I had two tumbles in my first hour on the board. I was consciously keeping my speeds way down and prepared myself properly for the anticipated learning curve by wearing a helmet, jeans, and wrist, and elbow pads. I was also wearing flat-bottomed motorcycle high tops with padded uppers and malleolus protection, which turned out to be a huge win if you can swing something like that (anything with ankle padding is a plus; don't wear anything with heels). I also set my phone up to video my practice so I could diagnose any problems. I chose pavement because it was perfectly smooth, even though it's hard. If I had perfect grass or astroturf I could visit, that might be better.
My first get-off was due to the training mode ("Classic"). A lot of people have said to get onto Extreme mode. I was dubious, but they're right. Here's the scoop. As near as I can tell, Classic mode merely caps total motor output. I made a sharp, slow turn followed by a demand for quick acceleration, and I exceeded the torque limit of Classic mode. Over I went. Good thing I had those wrist guards. The same turn later went fine in Extreme mode. As soon as you posses the capability to keep the board from accelerating and carrying you off into the distance uncontrolled you've moved beyond the benefits of Classic. FM has done everyone a bit of a disservice by calling it "Extreme." Don't be put off by it, it's safer. But, do keep your speeds way down early in your career.
My second tumble was a heel-side turn (left, for me, I ride with my left foot and the sensor up front - if you don't, all of the following info will need to be interpolated). The OW stopped, and I kept right on going. I checked the video, and sure enough my front toe clearly lifted up off the board. Once I knew the issue, I could focus on it, and it hasn't happened again. I'd bet that most of the problems people have are during heel-side turns because of the way the human foot moves, and doesn't. When turning toe-side, it's not hard to keep your heel down on the board sensor because your entire body weight is driving the heel down through your shins, even when you're pushing your toes down hard into the board to carve a turn. But, on a heel-side turn, the effort to maximize your weight onto your heels leads to a natural lifting up of the toes. The sensor is actually more forgiving than I'd have guessed, but if you don't consciously press down your sensor toes a little in a heel-side turn you're going to lose toe contact on the sensor. It doesn't take a lot of pressure, but this does seem to mean that heel-side turns may be inherently less sharp than toe-side turns, all else equal.
When I ride mostly straight or make toe-side turns, I'm riding with an elongated front leg (because the front of the board is lower when you're underway) which stays pretty quiet in movement. My rear leg, on the other hand is a very active cheetah tail. I flex my rear knee actively to control board pitch (speed), and I can really kick the board around the yaw axis quite radically to cut some nice toe-side turns. My rear heel is usually well off the board with only my toes touching so I can use ankle flex to help steer the board. The board is really fun and very responsive with this technique, for me anyway. But this technique doesn't translate to heel-side turns because I need that rear heel down in tandem with the front heel to roll the board over.
If any veterans have any advice as to how to get better heel side turns I'd love to hear it. Next time I go out I'm going to experiment with moving my entire body weight a little toward my heel-side to create a bias in that direction. It will be a little more tiring at the ankles to maintain a straight line because I'll need to lean toe-side a bit just to go straight, but I'm thinking I might tighten heel-side radii for when I'm carving.
A lot of words and pretty thick, too. Sorry about that. ;) FM has had some quality issues to be sure, but don't pass on it because of concerns over front sensor ergonomics. A bigger sensor isn't a bad idea, but one thing FM could do to make the board safer without a hardware change is a software change as to how board behaves when the sensor loses contact at speed. I won't rehash my old posts on that here.