I can't answer questions 2 & 3 for you, but I can give you my two cents regarding your first question. I bought my QX60 on 22 Feb and I've been very happy with it. I purchased an AWD Hybrid with the Theater, Hybrid Premium and Technology Packages. It is moonlight white with the Java interior and maple accents. I've only got 750 miles on it thus far, so I'm still breaking it in, but I've been averaging 21.5 mpg. I live in Los Angles county (for now), and I routinely change 900 feet in elevation every time I go anywhere (my house is at 1000 feet elevation). I also experience mostly stop and go city driving. By comparison, my previous vehicle was a 2010 Buick Enclave AWD, and I was averaging 13-14 mpg driving it the same as I do with my QX60. My QX60 is just as quite and refined as the Buick was, and I find the ride and seats to be more comfortable.
The only negative is it's a mild hybrid (which I knew going in) and it takes a little getting use to. For example, if the engine is off (EV mode) and you quickly hit the gas, it can take approximately 2 seconds to start and put the power to the wheels. So when you first experience it, the hesitation can be a bit disconcerting. That said, when you are at a stop light and the computer shuts the engine is off, it will start again when you take your foot off the brake so you can quickly learn to anticipate it (that's the getting use to it part). More often that not however, I find that the electric motor primarily assists the gas engine, rather than operating in EV mode, especially when you have the A/C on. When the engine is on, I have not experienced any hesitation. That said, I'm still thrilled to average 21.5 mpg verses 13 mpg in a similar size, 7 passenger SUV. The mpg I am achieving vastly outweighs any negatives. If I didn't have the elevation change, I think I'd be averaging closer to 25-26 mpg.
I have two girls (5 and 8), and they love the dual screen monitors you get with the Theater package. My wife and I like them also because they don't block the view of the rear view mirror. (My Enclave had the entertainment/nav system, and the rear monitor was mounted on the ceiling. When it was down, it would block some of the view out the rear window.) I can also verify that "Let It Go" sounds awesome on the Bose 5.1 surround system, even after the 20th frickin' time....but I digress.
I was seriously considering the 2014 Highlander Hybrid (I'm impressed with Toyota's hybrid synergy drive), but when we went to go look at one, my wife hated it. The interior "syntech leather" looked cheap in my opinion -- Toyota's marketing calls it "syntech leather"--I call it vinyl. I was under the impression the redesigned Highlander had an upgraded interior. Well maybe it does, but I was very disappointed. My wife and I thought it had huge perforation holes in the "syntech leather" seats, and I thought the second row captain chair bottom seat cushions were kind of low to the floor, and the arm rests looked flimsy. I was also surprised to see the floor slope up to the 3rd row, which resulted in the 3rd row bottom seat cushion being ridiculously close the floor, your knees would be under your chin.
After the disappointment with the 2014 Highlander, my wife wanted to look at the QX60, so we stopped by our local Infiniti dealer to check one out. (I had done my research, and was concerned about the supercharged 4 in the QX60 hybrid. I also knew the hybrid in the QX60 was a mild version, so I thought the SUV would be underpowered with harsh engine. When we looked at it in person, it was night and day different--the Infiniti's interior was vastly superior to the 2014 Highlander Platinum. I found all three rows comfortable, and after a test drive which eliminated any remaining concerns, I ended up driving it home. It didn't hurt that I got a killer deal either.
So have you test driven one yet?