So I've been using a Microsoft Surface as my primary machine (everything except software development) for almost two months now and I'm not having any problem with "gorilla arm". And I don't think most people will. The reason being that the only time that I need to touch the screen a lot is when I'm consuming content (reading blogs, watching videos, etc.) For that I ditch the keyboard and hold it like a tablet. When I'm creating things, i.e., e-mail, writing proposals and documentation, my hands don't really leave the keyboard very much. I'm typing this on my Surface and I'm not having any problems because there's no need to touch the screen when creating content.