I used Voice commander for a few months and it was quite ok. It is possible to control the background wow while you play your main : its an option in the voicecommander window. Forgot which one. With google, I found a forum dedicated to Voice commander and youll able to find the info there.

Ive been using Keyclone for the last 10 days and its much better. Of course, its much better for 3 accounts or more. But even for duo, Keyclone is at least more reliable. For duo, if u have a lot of micromanagement for your main like a rogue, wawa or warlock then VC would be perfect as the fingers on the main and the voice for the alt can be very well orchestrated. Unfortunately, VC is not perfectly reliable, I would say 95 %. And its tiring to breathe slowly, not to listen to music, not to scratch your head, to avoid any bad action in the microphone. Also, I read that VC has some issues with Vista. Dunno about that.

So, Ive definitely switched to keyclone with no regret.