Input is the reason tablets have not yet replaced PCs. Voice recognition technology is not yet a good replacement for keyboards. It is almost there, but not quite.
Output is going to be more of a problem. Google Glass and competing products are much more likely to be viable since you can see the output. Smart watches are going to need some sort of holographic or projection screen technology to solve the output problem.
These are the same reasons why calculator watches never replaced calculators, even though they were available 30 years ago.
I'm using Android 4.something, and darn if the VR isn't excellent. Probably 98% at this time. I'm working to where I'll take notes on the job with the phone instead of paper/pen.
That said, I recently texted a friend named Mitch. What he got was, "Bitch, can you meet me at ..."
But possibly my voice just interfaces really well for some reason. Had a heck of a time 15 years ago with Dragon, and a friend could use her's almost perfectly.