Rolled our own - one I helped write, one I used. Both followed a stripped down C-like syntax (minus pointers). Both had conditional statements, loops, variables, simple structs, arrays (range checked), float/int/bool.
On the projects I worked on script performance wasn't too much of an issue, the scripts were used to control state and flow, not to do any number-crunching.
If you control what is exposed to the scripting then engineering will know when design asks for access to something that should be implemented outside of scripts. Which in my experience seemed to have minimized performance issues.
One concerns when switching over to a development system such as Unity or Unreal 4 is that your gameplay 'scripts' have access to the entire engine. It seems very easy at that point for your game to turn to unintentional spaghetti.
