Unfortunately the unit still needs to turn to move, the script just turns it back.
So all this means is that the whole unit is a turret. The primary thing this does is make it impossible to determine the direction the unit is -actually- facing. Which is, um, really bad.
Physically, it is no different than just having a turret on a unit with a very fast turn rate. Basically all our bots behave this way, and frankly it makes them less interesting (it removes the physical mechanics of having a turning circle). Worse, if the unit turns -really- fast (nigh-instantaneous direction-change for the purposes of movement) the turret (IE the whole model) is going to lag behind and waggle around, you get this on the warrior and a lot of other units, you've probably seen it.
There might be a way to set the models direction independent of the unit facing itself (I suspect so) but that's still basically a bot.
More interesting is a unit that takes time to get up to maximum velocity, and then when it turns needs to accelerate in the other direction- it cannot convert momentum in one direction into momentum in another direction simply by turning (If you've ever rolled a car you know this is basically how they work anyway and that turning is a lie). This is how gunships operate, when you turn them they slowly accelerate back in the other direction. Hovers doing this would actually be something interesting and more worthwhile (Though, it may not actually turn out well or create good micro or mechanics).