If I wanted to use Android apps (I use to own an Android, I'd just pick up a cheap Android tablet. There a dozens of them out there. I've never heard of any OS emulators that didn't have a significant impact on speed, but I suppose if there was one useful app that only ran on an Android, it might push me to try. I'm pretty sure that's not going to happen.
Sort of defeating the point of Surface - your all-in-one becomes an all-in-two.
I could buy an Android tablet, I just don't want to carry it.