When you say you are walking 3 miles pain free, are you using crutches or a cane? I'm curious, as I am 4 days behind you and walking up to 5 miles a day, but definitely NOT pain free.

Stephen, everyone heals differently at different rates. I was hardly walking at all at 8 weeks. Now I'm doing pretty well. So long as nothing untoward happen with the surgery and the device is well placed I wouldn't worry about "slow" progress.

I wasn't pain free with walking until probably about 5 or 6 weeks, yet I did a lot of walking, probably too much.  There is that little bit of the stride that will still have some tenderness and it wil grow if you do too much.  That's why a limp is common up to 6 weeks or more.   

I'm with Danny on this, that we all have varying speeds of recovery.