That's looks surprisingly useable.
I was expecting it to be laggy and slow, but judging by what you said to Teehee, it's not.

The store is a bit laggy at first but that may be because my phone isn't exactly high performance (Samsung Galaxy Gio)
Everything else is really responsive and easy to use, which surprised me as well

Works well? Is it responsive? Does Mobile Steam have Voicechat?
No, at least I don't think so.
The options menu is empty at the moment.