Having been a GT operator for most of my 72 years, in 2008 I decided to buy my 1st ZTR. Half way thru the 1st full season with my new ZTR and having lost control of it twice, I was ready to park it out front of my home with a for sale sign on it.
With no control of the front wheels, ZTRs do require more attention during operation. As soon as one or both rear wheels loose traction, even if only for a short moment, it will go where it pleases!!!
As time has passed and experience has been gained, I wouldn't be without a ZTR, so even an old buzzard like me is able to be re-trained!!!
I still won't be without a GT as a ZTR is a specialized mower and does a great job of it, but won't do much else.
I recall years ago when I was going thru training for my private pilots license with a retired military flight instructor. He put a blindfold on me, let the aircraft stall, sat back and told me to remove the blindfold and regain control of the aircraft. A ZTR sliding sideways out of control reminded me of that experience.