Hi! Yup, I was in Vegas too and up at the barrier!!!! I have to say, I've been to many concerts up in front row in my time, but I wish to reinforce this statement: CAMERA PHONES HAVE MADE THE PIT EVEN SUCKIER! Now that people have digital cameras on cell phones, they pushing their way through to take a photo. In the good old days, at least lighters gave everyone the sense to give a bit a breathing room, otherwise the flame would set everyone's 80's big hair on fire! People made their way up to bask in the glory of the band, NOT to piss off those who earned their right of being in there by standing around all day to TAKE A DAMN PHOTO! I saw more people spending time behind their camera screen than actually STARING at the awesomeness of MUSE, who are RIGHT THERE... live in person! Also, please keep in mind of those who are short like me, that when you take a picture, to not jab your elbow in my face... someone almost broke my glasses! (can't wear contacts because of my prescription, so don't bother commenting please).
Also, I think if you stand anywhere, Matt's side will be the worst for pushing. I was on the side with Chris and most of the wave of pressure was moving its way from the left, where Matt was. Of course, this was Vegas and the underage crowd were partying it up and two chicks were even duking it out in the crowd near us fighting over a guy I guess. One poor girl even went into an epileptic seizure! Poor thing. Also, as solarbell said, you WILL sweat and get other people's sweat on you. Drink plenty of water during the day. Get drunk after the show. Don't bother with perfect hair and looking like a hottie for the guys. By the time you are done in the pit, your mascara will be down your cheek, the hair in a tangled mess and look like you have been through the "apocolypse" (I just had to say it). Put hair in a ponytail and be done with it! Plus, it will keep you cooler.
Also, bring hand sanitizer with you. You can get staph infections and other bodily fluid-transferred viruses from coming into such close contact with sweaty skin. Wear long sleeves and pants if possible to reduce your risk!
I agree... NO HEELS! Plus, they can stab another person's foot. Girls, wear Sheer Energy panty hose to keep the circulation going in the legs when standing around alot. I wore them and my trusty Keds and my legs felt great. I forgot my gel inserts, so my feet soles were a little sore.
Fairfax, VA (by Washington D.C.) will be interesting though. I went to three concerts while here so far and let me tell you, nobody really lets loose around here. I think this might mean that the pit at the Patriot Center will be more "tame" compared to other areas. I was at the Cure, and someone actually told me to please sit down so she could enjoy the show! (the pit had folding chairs for that show). LOL!