So, I finally got my N3DS XL (black) and here are my short impressions:
1. The unit itself looks beautiful. I love the fact that the color is more grey than black. Gloss finish looks classy, but it's kinda fingerprint magnet (if you care about such things - I don't). The build quality is great. Now that I have it, I understand how completely irrelevant SNES buttons are - you simply don't notice buttons when playing a game, so investing in a smaller unit for that reason is pointless (IMO). But, if you prefer portability, XL is definitely not pocket friendly (unless you wear cargo pants or carry a bag all the time) due to its size.
2. Screens are huge for someone coming from NDS Lite, but in the best way possible. I was pondering whether I should get the regular size, and I'm glad I went with XL. I played MH4 demo and I can't understand how anyone can play that game on a smaller screen. Same goes for Smash Bros.
3. If you have big hands like me, go with XL. I read that some people with big hands find regular one perfectly comfortable, but now that I've tried the unit myself, I find such claims baffling. The ergonomics are perfect and my hands would definitely cramp if I went with the smaller unit.
4. Super Stable 3D looks amazing. This is my first 3DS, but I've tried OG in a shop before and I remember that I was quite underwhelmed by 3D. Finding sweetspot was annoying and if I ever owned OG or OGXL, I'd probably play with 3D off. On N3DS, it's quite different, so I play with 3D constantly set to ON. There is some small flickering involved when you move your head, but it's nothing annoying or too noticeable. Best 3D effect I've seen so far is in Zelda: ALBTW.
5. C-stick works incredibly well. It's easy to use and more precise than I expected. Definite game changer for games like Monster Hunter. I fought 2 demo bosses and never used Monster lock-on. Didn't feel the need.
6. OS is quite nice and snappy, although eshop takes some time to load (I also received some error codes when trying to enter yesterday).
I'm absolutely loving this thing. It's comfortable, large screens are great, it's a definite upgrade over the old version. I've also noticed one thing; Youtube makes every 3DS game look crappy. When you play games on the actual device they look MUCH better.. I noticed this the most in Zelda and MH4.