Expensive if used every tick
Optimised if used sparingly
Do not activate/deactivate groups. That is slow
It's better to just run through 100 conditions, or more
Zvoc, probably, sometimes the easiest/least complicated solution is the fastest. But you'll never know if you don't profile it (e.g. with Microtimer if you don't have 2.5+)
Ian, it's not an issue if you do it rarely (we're talking times per game tick), once a second is 0.0166, that's classified as pretty rare.
The problem arises when you use that as state controllers so we're talking maybe 500.0 per game tick (activations and deactivations).