Doesn't adding conditions/restarts require your language to have stackful continuations? Those are quite complicated unless you don't bother to make them safe (like C doesn't bother to with setjmp/longjmp). I would be nervous about them for the same reason I am about exceptions.

Also, the restart seems to imply that you should "handle" the error, but I think this is really overemphasized cause what are you actually going to do about it? There's nothing to do about a lot of errors except die, but this encourages programmers to just make something up they think might help.