I have the G-Force with upgraded main shaft and case. I have only been to the strip once since install so not much history yet.
It shifts and feels like any other T5
Important to use a clutch that does not hit too hard.
From what I have been told if you have all the good internals the next weak link is the stock T5 case. The G-Force case is not expensive (relative to the gear set). If you are going to use a stock T5 case, some are stronger than others, so don't use the weak one.
Use a good shifter with stops like a PRO5.0
Don't forget the special fluid.
Choose your vendor carefully. I had very bad service from the 2nd source shop that supplied my G-Force. It was incorrectly assembled and caused a lot of problems and additional expense.
I wish I had gone with Bob Hanlon or one of the other recommended vendors I hear they do excellent work.