Penner tune is a great addition if you want to unleash the rocket's real power. The QS is one of the best I've experienced. TBH, I think it helps that the motor isn't super high-revving and gear spacing doesn't seem that great. Regardless it works very well and is better than the one on my current Ducati (or recent ones for that matter).
My biggest complaint is the lack of rear suspension travel (like many cruisers). That is why I avoided the GT because of the forward controls. I can lift my butt of the seat with the mid controls but you can change to mid controls but wait to add the QS after you decide what controls you are going to use as they each take a different kit. I did want the heated grips from the GT so added them later.
Take the time to dial in the suspension as well. I got the front nicely dialed in but still now happy with the rear shock so I'll probably swap it out. I am a bigger guy so that might be the issue. It doesn't help I have both sharp edged and/or big bumps so when I dial in the rear to be good on one type, it sucks on the other. More travel would have helped in this regard.