I just did a comparison between my 53cm road bike and my 53cm IRO. Seat tube is the same length, top tube is the same length, head tube is about 3cm shorter. No integrated headset on the IRO though, so that should account for some of it. I might have to get a bit more flexible, but the top tube on the 56 is too long to use without making the handling twitchy.

Edit: UPS guy just dropped it on my front porch after ringing the bell 3 times and walking away before I managed to run down 3 flights of stairs.. but he's a ******bag and does that all the time. Even on signature required packages.