Hi all
I have Nike Free 3.0 too. Had them about 2 weeks now and I've done about 6 or 7 runs in them ranging from 20 mins to 2 hours (today) but usually around the hour mark. So this a limited time / experience review...
Previously, I have used many different brands of running shoe and none of these have caused me injury either so perhaps I've just been lucky generally.
As Marek says, the Nike Free 3's are really soft, pliable and light shoes. How they cost so much for what they are God only knows but at least they are much cheaper than Newtons
The Free 3's are fun to run in but, to be honest, Im not usually thinking too hard about my shoes when I'm running.
After the first few times using the Free 3's I noticed reasonably tight calfs after the run too which were tighter the morning after. They eased off nicely after an hour or so, so not damaged, just tight after a nights sleep. After the 2 hour run today the most tired area again are my calfs but I have compression socks on now and they are doing the trick nicely. Will ice them this evening too.
I have been lucky enough to be doing a full winter of cross country racing this winter in spikes (no cushioning or support either) so perhaps I have been building up a bit of foot and calf strength generally. As others have said, if I was new to running I would certainly take it gently in these shoes, just so the old muscles can get used to not having built in stability or support from the shoes and build foot and calf strength.
Cheers
Neil