They haven't included an AC adapter in Japan for the 3DS models outside of the original Japanese 3DS. When they released the 3DS XL over there (and in Europe), they explained that most people would be upgrading from the original (considering how popular the original 3DS was, this was a fair assumption IMO) and did not want to charge users for something they didn't need.
Granted, this does not help those customers who trade in their systems. And yes, Gamestop does expect AC adapters with trade-ins of the original 3DS (hopefully they don't with trade-ins of the N3DSXL).
It's not a great policy, but I know that there are at least 3+ of those adapters floating around in my house, and we only have 2 gamers.
I personally wouldn't suggest judging the N3DSXL's screen on Xenoblade Chronicles 3D. I've heard from many that it's a bad looking port and that folks would be much better off playing the original Wii version. I was really excited about it and got the N3DSXL at launch but when I saw footage of the port, I gave up on getting the game. It looks terrible in comparison.
Other games, however, which can also be played on the regular 3DS, still look good. I was really impressed by how Monster Hunter 4 Ultimate looked, for example.
Nintendo has never been big on their graphics, but instead opting to focus accessibility for many. A less expensive system, easier for a wider range of gamers to use, and a much better library of games will always win over something that's much prettier to look it. Vita had a lot of potential but was trying to do too much. Younger users were returning their systems because they didn't know how to use the thing (and their parents certainly weren't going to figure it out). Older users were returning systems because there is no library to support it. The console can't be a success if they can't cover those basics.
I agree with the OP about the placement of the c-stick and general feel about the console and 3D itself. However, the SD card thing doesn't bother me. I don't download many games, though I had some from the Ambassador program. I had already done some research prior to launch of the system and bought a larger MicroSD card to have on hand so I wouldn't have to change cards out (I only had to swap out for a larger card once on my original 3DS). Thank goodness Nintendo is not using proprietary SD cards for storage, unlike Vita's ridiculously priced cards.
If anything, I just think Nintendo did a terrible job of marketing the N3DSXL. It's not an amazing system, but the improvements are nice, including the faster processor. I did a fair bit of research prior to launch and knew about the adapter and what to expect in general. To users new to the Nintendo handheld, though, I can understand the frustration of not having that information be more clear.