Maps with old vis will load normally but will have empty vis created, this will just mean you will have no vis culling when inside a room etc.
To get vis on your map again, a map recompile is needed. You should only have to recompile vis again, not a full lighting recompile. Hopefully this will be faster now and you can tell us about it.
This is a pretty big change so if any problems pop up, tell us and we'll get them fixed.
