Lots of people swear by rear steer lots of people don't. It's a personal preference thing. You should try it out for yourself.
Here is my take on it for what it is worth. The only time where I have thought rear steer worked well was when running tracks with very wide corners. I think on tracks where you spend significantly more time on the straightaways than in the corners (majority of tracks) the rear steer is a hinderance.
pmsimkins Is exactly right. it all depends on the lenght of the track. if the track is very long and narrow you are not going to want to run rear steer because you will have to constantly correct the direction of the car and the car will be scrubbing all the way down the lenth of the track. but if the track is very short and the majority of the time driving is spent turning the car then by all means put rear steer in there and try it out. I have never tried it because I just got into oval racing after road took a serious decline at my local track but I do hear that it is the hot ticket for the banked track since the straights are very very short and there is almoast no time when the wheel is ever allowed to return to netral.