Let me hear you say Yar!
I [heart] the fast prime lens on my Pentax; I didn't even try to use the flash when I went to the Captain Bogg & Salty concert this afternoon -- I just cranked the ISO up to just below the point where the sampling artifacts would leap out and strangle me (1600; the Pentax goes up to 3200, but the picture quality suffers greatly at that setting,) set the shutter speed to 1/30th second, then let the camera decide all by itself whether it was going sit, whimpering, at f1.4 or go up almost as far as f2.0.