It's a good motor, but it's not great. I have one and it is eclipsed by the Hirosaka and Killshot motors I have. In a GT12 one might find the Mach 1 a better bet.
I understand there are new motors coming from Reedy, so if you are tempted by a cheap second-hand one give it a go. If you want to splash the cash, keep it in your wallet for now. Not only are there better motors for GT12 cars now, but Reedy has rarely made their new motors worse than their old ones.