I'm just back from L.A.--managed to get home yesterday despite the hideous weather. I'd been to L.A. a few times since the Walt Disney Concert Hall opened in 2003, but I'd never visited it. I went on a tour this trip, and was just blown away. You can't really understand the power of Frank Gehry's building until you stand next to it. (This is probably true of the Guggenheim Bilbao, too, but I have yet to make it there...)
Next time I'm in L.A., I'll absolutely go to a concert at the concert hall, but I'd encourage anyone and everyone to take the tour (from $12) even if they don't have performance tickets. Info on tours is available here.