So for the Star Alliance MegaDo 4, the plane was advertised as being a reconfigured 767-400. However, as the FAA filing for the event was published, there was an aircraft substitution that was never announced to everyone. As everyone knows, sometimes that can be a bad thing, sometimes it can be a good thing. In this case, it was a very good thing. We were upgraded to the 787, which due to mechanical issues, United currently only has one while Boeing repairs the other. Thus, we were the first North American charter flight aboard this aircraft. While I'm not going to post a lot of pictures of the flight (there are way too many of them out there, and it was hard to get the really good pictures inside), I will give some thoughts on the experience.
You really feel the engines taking off on this plane. I mean seriously, the take off roll as you start launching down the runway is impressive, and feels really good. On most planes, it is kind of steady, but this one you really feel the acceleration. I was impressed. This is not surprising, since it has a reasonable amout more thrust than a 767, as well as being quite a bit lighter. Another advantage of this, is that the climb is much faster getting you to cruising altitude and out of your seats quicker. Below is a screen grab from flight aware that covers the first segment in full, and most of the second segment as far as speed and altitude.
The windows are something that everyone already gushes about, and after seeing and using them, I understand why. The ability to select how bright you want the window makes it quite pleasant to look out at the scenery without as much glare. Now these do not go completely opaque, so if you are light sensitive when you sleep, you should be prepared for a little bit of light. Now the surprise is that even the emergency exit door windows use the exact same control system. And all the windows (even the emergency exit door windows) are much larger as promised, and it is a size difference you do notice if you are so inclined to enjoy the scenery outside the plane.
One caveat I do feel I need to give with the configuration United has chosen is how the seats recline in economy. Unlike all of the existing seats on United's planes, these seats recline by pushing the bottom of the seat forward. This means your knees will get pushed forward. At least unlike some airlines with this configuration, they did have the decency to have a softer seat back, and give an extra inch of pitch. But if you can not deal with 32" of pitch and then having your seat slide forward, then you will want to be aware and get out of regular economy and into economy plus.
The entertainment system is standard, however as United is prone to do with the 787, they are pushing the dreamliner branding like crazy.
The branding push continues with fact cards in every seat back, as well as a special 787 introduction from Jeff Smisek before the safety video. However, on the plus side with that, there is no news about changes they are making that he thinks we will like ;)
And it did feel more comfortable because of the increased humidity, as well as the pressurization to a lower altitude. However the flights were short enough that we were not able to really get the full benefit, since the segments were 3 hours and 2 hours.