I saw Sep back in 2002 or thereabouts with Derrick on vocals and they sounded great. Definitely not a cover band. Andreas and Paulo (Igor was still in the band, but since he's not anymore I'll pretend like he wasn't) are fabulous musicians and play extremely tight live. It's not like you're watching some Joe Blow cover band -- these guys are pro's. Agreed that the vocals sound different, but the style is more or less the same... it's not like they got Dio to replace Max or something... even though that would be fucking awesome lol.
I love inside jokes, I'd love to be a part of one some day.