My JD 4710 has the same PRT tranny as available on the newer 4320. For the most part I think the JD PRT works great.
Upsides:
Range Shift: You do have to be stopped and clutch to shift ranges, but it's simple and fast - as it should be. Rarely it will be a tad balky at going into gear if the teeth aren't lined up just right and there's pressure on them (tractor parked on a slight slope.) Thinking about that - I think that has only occurred from a cold start park in the shed, not out in the field. (Shed floor is on a slope).
Tranny Shift: You can shift on the fly, using the clutch, the 4-speed tranny. Works fine, no issues whatsoever.
Shuttle: The (clutchless) shuttle on the dash works smoothly and positively. I don't shift between forward and reverse using the shuttle except at very low speed, although Deere doesn't specify a max speed it just doesn't seem to be a nice way to treat the tractor.
Speed choices have been fine for me - but I tend to piddle around fairly slowly. (I think I've used "C" range only a few times - rarely need to go that fast.) The gear spacing is pretty good. A4 is the same as B1 so it's really only 11 real choices - but it's actually handy to have that particular ground speed in each range, so no big deal.
Downsides to the Deere PRT:
Fundamental Design: The main clutch is a wet multi-disk pack (two packs actually, one for forward and one for reverse) hydraulically actuated. When you push in the clutch pedal you're actually just opening/closing, via linkages, a valve in a valve body under the deck. The shuttle lever just manipulates other valves in the same valve body. As a result of the execution of this design, there are two 'odd' effects I've found:
1) The tractor is not 'in gear' even when parked 'in gear'. Without engine power there's no hydraulic pressure on the clutch to keep it engaged. Seems to me that could have been designed the other way around to use pressure to release the clutch, then the default state would have been to be engaged. So no backing up the parking brake with the tranny, an old habit of mine on all other manual tranny equipment.
2) It seems to be more difficult to smoothly feather in the clutch when shifting or starting than on a typical manual tranny. The hydraulic valve goes from closed to open and the clutch engages within a very small fraction of the total clutch pedal movement. This is more pronounced when the tractor is 'light'. Under any kind of load the takeup seems just fine. Not that it's bad, it's just doesn't seem to be quite the same as a well-adjusted more mechanical clutch.
[Those issues may well be common to most hydraulic-shuttle set ups, I haven't studied any other mfgs on the details.]
No Creeper. When the 4000 series first came out, there was a creeper option. That disappeared with the 4000-Tens. A1 is slow (around 1 mph at PTO speed) but may not be slow enough for some very low speed work - such as tilling or certain spraying operations. Don't have a tiller yet so haven't been able to judge that aspect.