Most cars built in the last two decades have front and rear anti-sway bars. The TRD is an upgrade to the OEM rear. It is slightly stiffer, which causes the rear of the car to not lean as much, which allows the front to grip in a corner because of weight being shifted to the front outside tire. However, the consequence is less weight shifted to the outside rear tire, which can cause it to slip, and thus oversteer.
The TRD was made to slightly reduce understeer while still being safe as a daily driver (sorry Scott, but TRD engineers know what they are doing more-so than a generic suspension engineer).
However, where Scott is correct, is that oversteer takes skill to manage properly.
I hate understeer, in a daily driver and on the track. Once you understeer, you lose braking and steering, which is very bad, but it takes a lot to make a car understeer, so unskilled drivers usually prefer this (a good example would be to shift hard around a corner and chirp the tires. When the tires slip, the car stops turning, that is understeer).
With oversteer, the problem is that unskilled drivers tend to slam the brakes and over-correct when they oversteer (drifting is an example of controlled oversteer), which is about the worst thing you can do.
Personally, if you have never driven a RWD car, I wouldn't do it. Learning the hard way on a brand new car is never fun. If you have experience on a RWD car and know how to handle it, then you'll enjoy it.
