That's right, I have one installed on my 1994 3000gt 5 speed. I can safely say that this modification makes a night and day difference in the way the car handles. It is still possible to spin the tires, but they both spin and hook-up real quick. Torque steer is almost non-existent. But, I believe that is due to the unequal drive shaft lengths. (Not 100% sure about that fact though).
I also have not detected any wheel hop. I want to install some new hard engine mounts next year to see if more traction can be gained. If you really want to add more power to your car, this modification is a must. Or, if you want a safer car to drive, get one.
I am 100% happy that I spent the money (which is a lot) to have one installed. I would expect to pay between $500 and $1000 to have one installed by a transmission shop. I think it really depends on where you live. Half of the shops I called would not even do it and the other half required my first-born child or $1000.
Something else to consider is to upgrade your suspension components in addition to installing this differential. Worn out or weak components will also cause a loss of traction.
Cheers,
J