Went in 2009. By far the best festival I've ever done, and great value too. Haven't got the time this year but want to make it part of an Eastern European road trip or InterRail adventure next year. The Dance arena was ridiculous, just to name a few:
Paul Woolford b2b Yousef
Richie Hawtin b2b Dubfire
Sasha b2b John Digweed
Steve Lawler b2b Lee Burridge
James Zabiela b2b Nic Fanciulli
Loco Dice b2b Magda
Carl Cox b2b Green Velvet
Zabiela b2b Fanciulli and Carl Cox b2b Green velvet are well up there with the best sets I've ever seen. Both 6am-8am at the end of the first and last nights if I remember correctly. Pretty sure you can still find the sets with video footage online. Exit.tv in a google search should find them. Can't wait to get back there, Serbia is a beautiful place, really cheap, and the fortress is an unbelievable setting for a festival.