Hehe, the OP sounds a lot like my initial reaction to stripping out the ZS, too!
At first I thought I had completely unbalanced the car (95% of the weight was lost from the rear,) because I was getting so much oversteer round corners. It wasn't long, though, until I realised that I was getting the oversteer beceause I was entering corners SO much faster, because of the extra acceleration.
I timed my 0-60 with a gtech the other day, and I after a couple of runs my average was around 6.6 sec, with the best being 6.51 sec. I'm not sure how accurate the gtech is, but I tried it when the car was standard and I got a best of around 7 sec (IIRC.)
Bloody noisey though.