After ~20k miles on the wavetrack in my 02M 6 speed and having driven it in dry/wet/snow/ice I thought I would give my observations...
1) Very good, but not for everyone. Similar to a rear sway bar, if you're completely out of control or throw your hands in the air, stomp on the brakes and scream anytime the car does not do exactly what you want, then this is not for you - see item 4 below.
2) On the dry, I was shocked at how well it actually pulls you around/out of corners. I ended up clipping a couple curbs on the inside because the car just sucked in where I pointed it. On exit/entrance ramps, roundabouts, sweeping higher speed curves, you can steer it with the throttle at the limit. In combination with the rear sway bar it's a little more sensitive to throttle induced understeer compared to an open differential and RSB - as mentioned above, not for everyone, but if you don't push the limits you'll never notice it. Most emergency maneuvers don't involve significant applied power so overall this is lower risk than a RSB to the novice driver.
3) On the dry, you can feel it torque steer left/right in the steering wheel, but the car goes mostly straight - definitely reduces wheel spin, can more/less keep traction in 2nd gear instead of spinning the tire(s) at will with the open differential
4) In the wet or in the snow/ice with good snow tires (Hakka 5's) - this is where it can be a little dangerous to an appliance driver (someone who treats a car like an appliance - puts gas in it and forgets about it). If you stand on it in a low gear in the middle of a corner, you will go in a straight line and the steering wheel is just something to hold on to. You can apply some throttle through the corners, but not a lot - if you're paying any attention at all, you'll feel it push, back off the throttle and it will resume it's trajectory around the corner. It actually forces you to be "slow in and fast out" of the corners. Once you're most of the way through, you can stand on it and manage the slip/drift no problem. I've never experienced anything like what Birdman or PeterV describe in the posts above - it almost sounds like theirs locked both wheels tight and didn't allow any differential effect.
5) I have not driven it through any really deep snow yet, but the 750 foot lane that was 6" deep was no problem. Trying to play with it a little (after the lane was plowed out), I would drive with one tire in 6" of snow and the other in packed snow over gravel in a curve and it would just drive right through it. It didn't matter if it was a right or left curve (inside or outside wheel with traction). With my open differential 02J 5 speed, it would go through it, but would have a lot of wheel spin and you better have some momentum built up. I could stop in the middle with the wavetrack and barely spin the tires and drive out of it. So many other places in snow/ice where you don't need as much speed/momentum or as much wheel speed to get you through compared to an open differential since you always have torque to both front wheels, instead of one spinning up all the time.
6) I was pulling into the last parking spot at work the other day. On the end of the row, half the spot was dry pavement, the other half was packed snow from the plow about 6-12" deep. I got about half way in and was inching my way up the snow bank (didn't want to slide into the car next to me). Was just about all the way in the spot and goosed it a little and both front tires spun - one on dry pavement and one on packed snow.
7) There is no odd behavior - you can't feel it engaging/disengaging. No noticeable effect on braking/deceleration. The only thing is on a really tight turn (like a U-turn) while applying moderate power, you can feel a little inside wheel slip/growl, but it's subtle and you'd probably never notice it unless you were looking for it. On normal throttle, it's perfectly smooth, on full throttle it will push because both front wheels will be spinning. This isn't really a fault of the wavetrack, but an open differential would just spin up the inside tire, whereas the wavetrack will help pull you around the corner.
My car has ABS only, no other fancy electronic controls. The rear sway bar is a good combination with the wavetrack.
5 and 6 are the reasons I chose the wavetrack over the peloquin/quaife
Not cheap, but definitely more advantages than disadvantages in my opinion.
