Well I have flown for nearly 200 hours with an O-320, with WW 151 prop, and Sam James Cowl.
I climb faster than an O-360 with a fixed pitch, and slightly slower than an O-360 with a constant speed. But keep in mind that you will likely NEVER climb out at maximum. The deck angle to get these extreme climb numbers is so high that I only used them in flight testing. When I am going somewhere, I climb out initially at about 100 kts, and then convert to a cruise climb of 120 KTS. I consistently see 1500+ feet per minute, tapering off as I climb.
As for Cruise, and Top speed, my plane is faster than many o-360's and slower than some. Top Speed for me is 178.2 Knots (based on spreadsheet), which is just a tick slower than Van's numbers for a 180.
I can vary my cruise numbers (fuel/speed) from 8 ish per hour in the 165 KT range, down to 6 gph at 145 kts, depending on how fast I want to get there, and if I need to stretch it to avoid a short leg fuel stop. I have cruise home at 170+ kts to beat an approaching system.
My cruise flows and speeds are within a few knots of an O-360.
In my opinion the difference is way overated. I would note however that I have flown an O-320 with a fixed prop, and it was a bit doggier on takeoff roll, but still fully capable and more capable than the certifieds.
The O-320 has been easy to cool, and I can climb directly to 8500 feet without any temperature limits. I have limited the baffel entry into my oil-cooler mini-plenum, and the result is that in the summer it runs at 185 all the time, and in the winter is never bellow about 150 degrees.
It is my personal opinion that the O-320 is smoother...shorter stroke.
Oh, and the longer mount, plus longer prop hub give it a more long nosed appearance which I think is awesome!
Here it is in the finished thread:
http://www.vansairforce.com/community/showthread.php?t=1744&page=23
http://img183.imageshack.us/i/dsc00427e.jpg/
And the for sale thread
http://www.vansairforce.com/community/showthread.php?t=63345
JC