Svnla:
First off I haven't seen Delirium so I'm judging by what I've seen on TV as well their web site's video previews. I've been to numerous Cirque shows, both in Vegas as well as touring shows in Chicago. They have ALL been incredible experiences that, for me, have been well-worth the high ticket prices.
With that said, Delirium does not look like a typical Cirque du Soleil show; it's billed as a "Live Musical Concert" so the primary focus will be on the music, with coordinating dance and visuals as well. My experience with their "standard" shows has been that the focus was on acrobatics/tumbling, trapeze and feats of extreme strength and flexibility that you would not see elsewhere. The staging was also unbelievable. The accompanying music has always been great as well, so I think they have pulled that element out and made a new show with music as the leading character. I expect Delirium will be lacking the "wow" factor of elaborate staging, extreme human performances, and an underlying theme/story that serves as the glue to mold all of the different scenes together.
I've never seen a bad Cirque show. For me personally, however, I'm taking a pass on Delirium and saving my money for Vegas or another future tour.