I've been spending a lot of time playing the Battle Frontier recently, and it's been pretty fun. I've spent the most time in the Factory. I think the NPCs are retarded, though. Recently I was in a position where I had a Steelix and the other guy had a Lanturn with Surf. The guy knew perfectly well that he could wipe me out with Surf, but instead he seemed to think it was a better idea to spam Attract when we were both male. Then I blew him up. So now I don't bother predicting. I just predict that they'll do something stupid.
Other than that, the rest of it's pretty cool too. I really like the Pyramid, though since I just recently started a new game file I don't have any Lv. 100 Pokemon yet (And all my EV trained Pokemon are Lv. 70...), so whenever I fight anyone their Pokemon are like 20 levels higher than mine...but I still win.
When I'm not in the Factory or the Pyramid, I spend most of my time in the Tower. I have a Modest CM Latias that destroys everything. It's awesome (Tank Regice is pretty cool too without the existence of Stealth Rock).
I haven't really explored the other facilities yet, since I never really got into playing the Battle Frontier when I first got the game, but I will soon.
To lurk in shadows, to live in darkness...that is my destiny.