Trivium are a band that hadn't played Belfast in nearly a decade as far as I can see, so there was a bit of hysteria when they announced to play Dublin/Belfast back-to-back. It was sold out soon enough, which makes my job harder when I'm trying to get about the venue for social shots and just general performer shots. But if you didn't have a packed out crowd, then the atmosphere and overall experience would be dampened, so it goes both ways in that sense.
But I guess it's a photographer's job to complain; if it wasn't the large crowd, it would inevitably go to the lighting. Whilst we're on the subject, I was spoiled with light for Trivium, with bright stage-facing lights allowing me to boost the shutter speed all the way up to 1/1250 very briefly! And when you combine the ability to shoot a high shutter speed with varied colours you can get some cool effects.
Another small issue was a number of people crowd surfing; which I have no problem with, in fact I encourage it! Images of crowd surfing is a great indication of atmosphere. However, the photo pit was 3-4 feet deep, with at least 4 photographers fighting for space, 3 security men and a barrage of flying limbs and feet due to the crowd surfers getting passed to the front, it certainly made concentrating quite hard!