I have the panasonic ZS3 and I've taped several electronic music shows with no problems. Now some people will tell you that the audio from the camera "isn't the best" but I can tell you it does better than pretty much any other camera out there. You don't seem like an audio snob so I think it will be completely acceptable for you.
Take a look at some of my videos. Especially the Chemical Brothers, the sound was SUPER LOUD there. These are just the regular files from the camera in 720P.
http://www.youtube.com/watch?v=i2Wr3O89O9Mhttp://www.youtube.com/watch?v=sulxRm7n01gI also taped the show with a dedicated audio recording rig and I feel the sound came out better on the camera than it did on my rig. Also, you don't have to mess with any post production syncing up the audio and video which is not only time consuming but pretty expensive if you don't have the right software. I can't stress enough how awesome the mics are on the camera. I've never had an distortions or anything and the sound has always come out crystal clear. Most audiophiles don't like it because it is only 192 kbps mp3 but, who cares? It sounds awesome. It's pretty idiot proof and sounds great imo.
You won't have a problem getting the camera past security since it is a "regular ol camera" and not some professional camera.
I don't recommend the ZOOM because it is not HD and frankly the video files are pretty inferior to the panasonic. If you go with the ZOOM HD you will get a good blend of audio and video quality but the zoom records with a fisheye lens and I prefer the wide angle lends of the panasonic.
For your budget and your audio/visual needs you definitely want to go with the Panasonic. I got mine off a guy on craigslist for $200. Then you should get a 16GB Class III SD card = $100 on amazon, and a backup battery = $10 on BPCamera.
Out of the shows I have taped, I can get up to 70 minutes with minimal zooming.
Also, I think you should really try to tape complete sets. I have shows to trade.

Who are you excited about seeing at ULTRA?