I have one. It's okay but I don't use it much. I'd use it more if it could run the games I wanted, but that's armshit for ya.
It would make a decent portable pocket PC. Also wish the screen was higher res. I added Openbox as another window manager option and spent some time configuring firefox to give me more room.
You'll find yourself configure things by text files a lot for software where you'd normally use a GUI. For example some addons in Firefox create settings windows that are larger than the screen. You can move them around in the default environment as long as the keys are all working (this is not sure, some times I have had to use setkeys or loadkeys because it simply decided to randomly not load the special key functions that boot).
I'd use it more if it could run the specific games that I want, but like most armshit the GPU doesn't have full OpenGL, so you're stuck to software, and the thing does not have some fast quadcore CPU.
But it's the only thing for the price with a screen and keyboard so it's okay.
You can get additional software using various repos for PI shit. For awhile I was remoting into it using x2go from a pi repo which was really nice when setting up a different WM and getting everything comfy.
Without directly comparing I'd say its as fast as an original PI Model B.
If I got bored with it and wanted to find some daily use where I could just set it up and let it go, I'd probably try to use it in my car as a dashcam system.