So I've listened to this enough to form some opinions on it. Off the bat, I like it a lot. Aside from that:
Tony Levin seems to have gotten over the intimidation. Unlike the first two, where he was pretty much a non-factor, he's my favorite part of this.
The second disk is far better than the first. Disk 1 was clearly an effort to make an LTE album. It honestly seemed formulaic to me. Beginning with Hypersonic, which is the "alright, let's do the really fast, heavy opener now" song. Some of the songs are very good, and Key to the IMagination is fantastic, but overall it felt inorganic to me. The jams were the exact opposite, though. That's just four super-talented guys having fun together. And doing away with the awkward beginnings and [mostly] endings was great.
It took a while to really sink in that it was JP/MP/JR jamming together again for the first time since the unpleasantness. During the jams on D2 is where it really comes off well. They've still got a rock-solid connection between them, and it's great to hear it again. I see people complaining that there weren't a bunch of key changes. To me that's part of the appeal. It's not monotonous when you get to hear these talented bastards finding new ways to play off of each other. I could listen to that sort of thing for hours.
Rhapsody in Blue? Honestly? We've all heard and/or seen it before, and truth be told, I didn't think it was all that good the first time. And after hearing the ideas they were cranking out on D2, it was definitely a waste of 13 minutes. If they really wanted to revisit the whole "prog band does Gershwin" concept, they should have adapted An American in Paris. That would have been kick ass and an excellent followup on what they'd already done. I don't know if it would have been as good as something developed from the D2 jams, but it would have been far better than just rehashing something they'd already done.
I didn't have any problem with JR's leads, but from D1 none of them really jumped out at me much, either. There were times during the jams on D2 that did, though. Moreover, I was probably more impressed with some of his tone choices. There were times on both disks that he absolutely nailed it. I'm really more about atmosphere than flash, and I think his contribution here worked for my tastes.