I have never bothered fitting one to my car as it's only ever used on the road and I don't think it would make enough difference if any to warrant the cost. Plus I have 2 mates that bought them, one says best thing ever and the other says total waste of money !

With 400+ hp RWD and a good diff and suspension set up I've never had any handling issues on the road !

Would i fit one if I was tranking the car ? Yes is the simple answer.
I belive that it would make a big difference here but I can't drive the car like that on a the road to need a 6 degree beam.

My way way of thinking is, If you have issues with handling and think a beam would improve it then buy one.
If you have no issues but everyone is telling you it will drive so much better with a beam then unless you just like spending money leave it alone.