I was waiting for someone else to post, haha.
I wasn't feeling very much like going crazy last night, so instead of my usual fighting for a rail spot, I sat in the center of that banister/wall/whatever you'd like to call it behind the floor. Perfect view and the sound was pretty clear, even if the guitars were a little muffled. The pits weren't crazy all night, but when they broke out they broke out. The Wall of Death during Exodus was a nice touch, and there were some nice circle pits (including one where there was a 15+ person pileup, which was amusing to watch cause it didn't seem like anyone could get up).
Mutiny Within: I had a pretty similar response as you did. They weren't fantastic or anything. I can confirm that the vocalist announced "Oblivion" before the song, too. Also, I think his harsh vocals sound a bit too forced. If he only sang clean I think the band would be a bit better.
Arsis: Same here, too. I love Arsis, and I've wanted to see them for almost 4 years now. But there WAS something off with the crowd and with the sound. I didn't recognize #2 either, though, so I can't help ya there. It was awesome to finally hear "A Diamond for Disease" live.
Exodus: Good, but I dunno, there just was something lacking for me. I was really tired at the time, though, so that might have been it. They put on a good set and the crowd was really into them, but I just couldn't get into it.
Arch Enemy: After a damn 40 minute wait, they did a great job of outshining the rest of the bands performance wise IMO. "The Immortal" was a brilliant opener, and...well, it was just an awesome set overall. I would definitely like to see them again (a change from my perspective at the start of the set, where I figured this was my chance to see them but I probably wouldn't go out of my way to do it again).
Good show, probably would have been great had I not started off exhausted. Bought an Arsis t-shirt and a copy of "Starve for the Devil", which they have copies of at the merch stand though it's not out for another few weeks. Still haven't checked it out though.