It's a lovely unit, nice bright screens (about twice as bright as the old DS), though it didn't come with the strap and thumb stylus that came with the original. It's black and shiny like the PSP, but the build quality is nothing like as good.
New Super Mario Bros. is pretty much the same as the SNES Super Mario Brothers. The only new features are Giant and Tiny power-ups that make Mario about the same height as the screen or half the size of normal Mario respectively. The tiny power-up allows Mario to fit through small holes and reach otherwise inaccessible areas.
Dr. Kawashima is quite a phenomenon, breaking the usual mould for best selling games. I have already noticed an improvement in my mental arithmetic and it is particularly enjoyable playing with more than one user, as your daily efforts are comparable with your friends'/family's.
The DS is a great toy and I've spent a lot of this weekend playing Mario.