After Eight - 55% gross potential is a very solid week for a first preview. Many long running shows (Phantom, Mamma Mia, Mary Poppins, Chicago, etc.) frequently have weeks below 55% gross potential. Even so, previews are heavily comped and 55% is actually quite high. If you'll remember a few months back, Lysistrata Jones was performing in the teens and Bonnie and Clyde was hovering around 30%.
Also, I think it's ridiculous to make any judgments on grosses for only 8 performances when there has been no chance for word of mouth to spread and there are no reviews out. You can take your pessimism and unjustified hatred for new musicals back to the Once preview thread. It's really missing your commentary.
Scratch and claw for every day you're worth!
Make them drag you screaming from life, keep dreaming
You'll live forever here on earth.