A few comments having talked to the chief engineer when I was at the event (These are personal opinions, just to remind you haah):
1. Non box frame: The Toyota engineering team considers this a good thing, not a bad thing (as do I having wheeled my 06 a LOT). The frame is strengthened where it needs to be in order to support loads, however, the flex essentially acts as an extra ~1" of travel. For example, if you look at the picture in my "Other Interesting Features" section of the write-up on EE, you can see how the bed flex helps, in that position, if the bed was boxed all the way back and super stiff, you would be three wheeling. The bed flex allows the wheels to stay on the ground there. I know its not much, but it has helped quite a bit when I wheel. and I have not seen any downsides to it, as the bed is strong where it needs to be.
2. Seats: Not sure what you mean about the seats, or are looking for, so I cannot really give opinions. My 06 seats have served me well and they do have lumbar support adjustment knob, so not sure the complaint there, however, I do know they only offered cheap seats back then. if we wanted leather, we had to do special swaps. Now with the new 2016 (maybe older models as well, never looked), they do offer "premium" seats that are leather. Maybe they have better adjustment as well? not sure, but they were nice in leather. haha.
To be honest, going into it was not that excited about the new truck. Like everyone I was pissed they didn't offer diesel, thought the front was ugly, and not enough useful changes. But after going to the event and talking to the engineer, a LOT of things became clear. Here are a few examples that are behind the scenes that normal consumers (including me) never realize that constrains them so you can get an idea of what they deal with.
The new café laws go into effect and are based off vehicle weight. They also get more stringent every year, so Toyota has to design for the future. Someone mentioned Nissan using the titan frame (this was actually a specific example the Toyota engineering's talked about). While that works great this year, and possible next year, that truck with that mass will no longer meet the café rules in a few years, so they will have to either keep making it larger, or go back to drawing boards.
It's the same deal with a diesel. Mike (the chief engineer) wants to drop a diesel in there just as much as we want one, but in order to pass current emissions, it would take over a million dollars invested into it to allow it to pass (yes they have actually looked at this and got the numbers, I mean it when he wants to do it haha). The problem is, that would only pass for 2 more years before it would fail the increasingly stringent laws. So, if they did it, first off you would be getting a neutered diesel (not the hilux engine we all want), that would only be legal for 2 more years. The large trucks can get diesels because again, the laws are weight dependent, so the other option is to keep increasing the size of the Tacoma, but as we all know, that is also a sore spot for most people.
Basically, after talking to the engineer (who ran the Baja 1000), it is clear he knows what off-roaders want, as he is one. And if it was up to him, he would make it happen, but there is a LOT of red tape in the US that stops a lot of great things from happening.
All in all, as with other people, to be perfectly honest, I will keep my 06 because it is a great truck and I've poured a lot of time and sweat into it, and there is nothing in the new one that stands out enough for me to upgrade. That being said, if I was in the market for a new one...I would def look at this one. The cab and interior is 10x better than my 06 (maybe not such a huge improvement over later models like 2015 version...but I'm still running an old 6 disc changer with no screen and a aftermarket Bluetooth module that dies more than it works haha)