Depends on what you mean by "mobile friendly!" Everyone tends to have different definitions. If you mean, responsive, not at this time. It is something that is slated for the future, but there's not a timeline for that at this time. However, the site is still easy to use and navigate on mobile devices. You can see my site (elise.internal.ithemes.com) which is built on Builder and determine if that fits your definition of mobile friendly.
I'm not familiar with WPTouch personally. We do have a Mobile Plugin as well.
Let us know if you have any other questions.