The DS Lite is not a major upgrade from the original model, but it sure feels like it. It is easier to hold since the shape is more uniform, and the stylus is thicker, more naturally pen-like.
The shoulder buttons are also excellently clicky. I was never satisfied with the clicks on the original DS (or the SP, for that matter)... they were a bit mushy. These buttons do seem like the kind of plastic that will discolor over time, however.
You're going to want a protective carrying case for it right away. I wish we could get away from glossy finishes on this kind of junk, because it creates an aura of fragility that I'd rather not have on all of my portables.
The GBA slot cover is not a door, as I had previously thought. It's a fake cartridge with contact points that completely plugs the hole. Although it's only about 2/3 the height of a GBA cart, so yeah, they do stick out a bit. Of course, I think the last GBA game I played was a year ago, so I'm not too worried about that. Once the Lite becomes the defacto DS model, I hope Nintendo comes up with some kind of flash cart chip that fits flush in that slot... for use to store demos and whatnot.
The on/off switch is totally weird, and I have not seen it mentioned anywhere else so I'll bring it up here. It is shaped like a sliding switch, but it doesn't have a distinct ON or OFF position. It always rests on the south side, returning to that position after you thumb it upwards. I'm not sure what the advantage is to that.
The screen is insanely bright. A huge upgrade over a screen that never bothered me much in the first place. The WiFi settings transfer was super-painless.
Overall, the Lite is just frickin' beautiful. If Nintendo had launched the DS with this puppy back in '04, you wouldn't have heard half of the bitchy complaints and whiny doom predictions.
As for Brain Age, it's interesting enough, and I can't believe I'm actively playing a game that tests my working knowledge of multiplication tables. Nice system of gradual unlockables, so you keep coming back to see if Dr. Kawashima has anything new to give you. Plus, I'm enjoying sudoku more than I thought possible.
The actual age test itself seems a bit of a sham, more of a clever scoring conceit than any actual medical science. I reduced my brain age from 56 to 22 inside of one day (20 being the optimum score.) So either I'm super smart or this is just a fun little non-game game, the virtual equivalent of those math/logic/word puzzle mags you can impulse-shop off the checkout counter racks.
Aside: that is clearly not a DS Lite in the picture of Clark above. That's a miniature DS water toy I imported from Japan. "Imported" being the fancy way of saying "ordered off a website."