it is pretty cool, and lasts for many hours -- bands, art, a tent for viewing short films and digital art, etc., etc. Yes, there is food and beer/wine, and some souvenirs to purchase.
last year, after the outdoor gig ended at cyberport, everyone went inside for dancing - it was pretty fun. no bad vibes or attitudes... even my horrible dancing wasn't criticised (to my face!)
the shuttle buses were cool getting there, but I took a taxi back to Central - I couldn't find the shuttle buses after I left to be honest
not that you need a warning, but there were a lot of persons who didn't pace themselves last year and ended getting burned out by early evening...they missed the late night fun. Drinking in the hot sun can get exhausting.