Think of it along the lines of hardshell RTT vs softshell RTT. If you're familiar with the tradeoffs between the two and you land on the side of wanting a hard shell, the J30 offers some improvements.
Here are some of the specific advantages I'm referring to:
-you can enter the tent with an external collapsible ladder, and you can also enter the tent through the JK with the middle panels removed.
-you can stand in the tent with the middle panels removed, particularly nice for changing clothes etc.
-as mentioned above the integrated top allows awesome aero, I also run a roof rack for lightweight items on mine, as well as solar panels. I've seen some hardshell RTTs that can do this, but not as efficiently
-keeps the weight lower
-depending on options you select it has 12v lights, usb ports, etc, that run off your vehicle
The biggest con I can think of (that any hardshell RTT will suffer as compared to a softshell) is the lack of space. For two people it is cozy, but we can no longer have our 85 pup sleep with us like we did in our old standard softshell RTT. She sleeps downstairs.
Like many other tents the stock mattress is a bit unsupportive for my other half (I am fine with it), so I cut a mattress topper in the shape of the stock mattress panels and now we are fine. We can still keep the bedding in there when we shut the tent too, but it does make it a bit difficult.
To correct the dude above, you can for sure run awnings. I have the ARB 2000 off to the driver side and a 1250 to cover the kitchen in the rear. Ursa Minor sells the brackets to do this, or you can DIY
Overall, I couldn't be happier owning the J30. Super easy to use, luxurious for sure, and I appreciate how integrated it is into the stock functionality of the JK.