I have had my Frees since May, and they aren't worn out yet, you can get some pretty good miles out of them. I don't do all my training in them, but I was doing about 40 miles per week in them at the height of my mileage this past season. They are very comfortable, and it really does feel nice to be able to move your foot. Assuming you have an efficient foot plant, you really don't even notice you are wearing the shoe. The heel height isn't as minimal as true minimal shoes, but I don't think that makes too much of a difference.
I haven't had major problems with PF in the past, but I have had more than my share of shin maladies, and I find that running in the frees actualls helps get rid of them. They almost force you to run efficiently, because it makes it a lot harder on your legs to land inefficiently. As long as you don't start trying to do all of your mileage on them at once, you should be good. Maybe start 50/50 and see how you feel, then increase it.