I was already accustomed to walking in minimalist shoes and had been running a few short runs in them, so there wasn't as much need of a transition phase. But the first few times I sprinted I only did four or five sprints, and not at maximum speed. It's probably a good idea not to overdo it, and then gauge how you feel the next day.
I am collecting all primal friendly restaurants all over the world to build a "michelin guide" for all traveling groks. Help is greatly needed! Please check the following thread: http://www.marksdailyapple.com/forum/thread76121.html
Here is an update in case anyone comes across this feed and finds it useful:
I sent back the Spyridon 46 in exchange for the 47's and it makes very little difference. The size chart on the website says that 47 is for 12 inch feet, but mine are only about 11.5 inches long. Also, my feet are flat, and now that I've worn them for about ten minutes I find that that they are most uncomfortable on my arches. They are a great design, the materials are cool (and look quick drying), and the sole is awesome, but they just don't fit my big flat feet. If you have normal feet they are probably great shoes, but if not, keep looking.