I see all GBA buttoms there (A, B, L, R, Start and Select).
This one is actually smaller than the previous renditions. It's the size of one of those tiny cellphones (yeah, the screen is smaller as well). There is talk about it being able to read SD cards and play MP3s out of the box, but I have yet to see it confirmed somewhere.
I don't see that much point for it either, but maybe it's to give the GBA some more exclusive features in relation to the NDS in order to boost the sales or something. Or it's just that Nintendo likes to makes things smaller whenever it becomes viable (the orignal Gameboy had 3 versions as well).