What if the user doesn’t have a Skuid license assigned to them? I would imagine  then the skuid page wouldn’t load for them. 

That’s a good idea for production but sandboxes don’t have licensing management.

What about setting the sharing settings on the skuid page object to private? You could add the users who don’t want/need skuid to a group with those settings.

Oliver, you’re totally right — this is difficult to do in Sandbox environments. In Production / Developer environments the easiest way is to remove the user’s Skuid license, but in Sandbox you basically have to rely on Page Assignments to achieve this, which does not scale well when you have 100’s of objects / scenarios where you’re using Page Assignments.  

So, outside of us adding a feature to Skuid that lets you globally turn Skuid on/off for a particular User/Profile (which we were discussing this morning in reference to this post), we recommend that you use Page Assignments and then use Mass Update to quickly switch all Page Assignments for particular User / Profile to “Use Standard Layouts” if needed.