So-far so-good, the JK seems to be a really nice machine.  After a couple hundred miles of screwing around, here's my impressions:

• New engine (3.8 liter V6 vs the 4.0 liter inline 6) is fairly similar.  Torque was available at about 12 rpm with the old engine, now it's more like 900...  I've stalled it quite a few times, still trying to get used to giving it some gas to get going.  Overall not bad at all.  Not exactly an overabundance of power, but I don't feel like it's any worse than the TJ, and it's probably a little better over all.  Maybe someday I'll go insane and get the AEV V8 HEMI package.
  
• The JK is way, way quieter on the road.  I have a 26 mile each way commute on highway 93, and it's nice and quiet now.  Still some road noise, but drastically reduced from before.
• The doors shut with a reassuring thunk instead of a rattle.  You can still remove them, but they are more like "real" doors now.
• Power windows...  good and bad.  Good in that with a 4-door I'd be annoyed trying to open and close the rears if it's only me in the Jeep, bad in that you need to have the key in the ignition to do anything, for instance if you're sleeping in the back and want to open or close a window at night.  Seems like a good trade-off though.
• The headlights are great.  As most people know, TJ and prior Jeeps had pretty poor headlights.  There's a bunch of upgrades that help, but they still suck.  The new fog lights (which I think look like the headlights on the Millennium Falcon when they're escaping the worm on that asteroid.... anyway...) are nice, they only light up about 10 feet ahead.  Low-beams have a nice wide pattern and are very bright, and the high-beams are, well, high.  The three sets of lights work together very well.
• Freedom Top is great -- you can remove the area above the driver and front passenger easily, and the panels fit in the back.  No more suckering friends into helping you remove the top just to get a little sun.  Ideally there would be two more panels over the back passengers, but oh well.
• Keyless entry... really getting spoiled now.
• Air conditioning is a separate switch from where the air is going.  No idea why it took so long to fix this, but you used to only be able to have AC work on the upper or upper+lower vents.  Now there's a dial for where the air is going, and a button to make it cold.  Nice.
  
• The back seats fold down flat (or at least pretty darn flat).  And there's enough room that if I slide the front passenger seat forward a little I can lie down and stretch out in the back.  I slept in it two days over Labor Day weekend, it was great.
• The 6-disc changer can actually read burned CDs.  My TJ would only play the first few songs on a burnt disc, then it would freak out and eject it.  The new one even plays MP3 files, and can read DVD-R (didn't try +R but they might work too) discs with MP3 files... and I can get about 800 files on a single-layer 4.7GB disc at 192Kbits, so that's 4,800 or so songs if I actually stuck 6 DVDs in the changer.  I have not tried a dual-layer DVD yet.  This and free Sirius/XM satellite radio for a year.
• A few mpg better gas mileage.  So-far I'm getting 18 or so mpg, with a mix of highway, trails and in-town driving.  Still not fantastic, but it's better.
• ABS, traction control and anti-roll programs, apparently from Mercedes (like the 6-speed transmission for the last few years).  Havn't really had a chance to try them out, other than weaving around on dirt roads, but hopefully it'll help in the winter.
• No limited slip diff in the back (which the TJ Rubicon had), though the new diffs and axles are supposed to be stronger.  LSD would still be nice, but in theory traction control should do essentially the same job, and non-LSD diffs are simpler and should last longer.... we'll see I guess.
  
• Still drives a lot like a tractor :-)
  

Overall I am really happy with the new Jeep.  Sure it's less Jeep-like in some ways, but it's just as capable and does it with more comfort and safety.  Just a great improvement over the TJ.