Had the heated grips on a snowmobile. Worth every penny there. (Don't own the machine anymore.)
Don't have them on the ATVs, can't say I miss them for that application. Not the same length of time (or speed) in super cold weather as on the snowmobile.
I'm not opposed to them, just don't see them as a deal-breaker when looking for the next ATV. If they're included in the right deal, fine, but I'm not paying extra for them.