Playing tuned down is usually fine as long as it's not stupidly more (more than a step) or Seek and Destroy. Tuning up never works. Listen to anything Priest did with Ripper live, the Halford material sounds fine but the stuff in C is neutered. Tuning up 1.5 steps would sound unbelievably shitty. Furthermore, any band that actually uses different tunings can afford to have multiple guitars for the different tunings.
EDIT: This goes triple for anybody playing arenas.