I bought one when they first came out, it's pretty awesome and has pretty much replaced my Nomad. However, it is a cheap Chinese clone system so it has issues.
Good:
The screen really is amazing, especially if you are used to the Nomad.
The system is pretty small.
Battery lasts a good 5 or 6 hours and is charged through a mini USB cable.
Bad:
D-pad button is awful, but you get used to it.
The sounds in a lot of games are off. Streets of Rage 2 is unbearable.
Some games simply don't work.
Mono sound only (even with headphones.)
Overall, I think it's a better portable than the Nomad since it's smaller, has good battery life, and a good screen. The sound issue is the real killer, I wish there had been a newer revision that had fixed that.