I live in the Uk and it's the first time I've seen or heard of them....
My daughter's got the N-Gage a portable games/phone system and i'm guessing it's a bit like that as well as the PSP...
I have played with one. It's a Windows system, which means that it is very slow to start. OTOH, so is the PSP, and that's selling like crazy.
The best thing about Gizmondo from my perspective is that it has a 2D shoot'em-up, which is not common on new systems. It is also very ergonomic.