According to MacWorld it is.

“The 27-inch 3.4GHz Core i7 iMac with SSD is the fastest Mac we’ve tested. The previous Speedmark 6.5 record holder was a build-to-order Mac Pro with a 3.33GHz Xeon Westmere six-core processor, 8GB of RAM, and a price of $4074. Add a 27-inch Apple LED Cinema Display and the price jumps to $5073.”

You can read about it here.