Divineo China now have the GBA Micro in stock, heres the details from them:

The Gameboy Micro is the smallest portable console ever made by Nintendo. It is in fact a micro Gameboy Advance SP, as it is 100% compatible with all GBA games and it has all the features of the GBA SP. BUT it is much smaller, much lighter, and the quality of the screen is simply amazing. Imagine it is 3 times lighter than an Ipod!