When I started running I used Progrid Guide 3 shoes. I made an easy transition to the update Guide 4 shoe the following year. Needing a new pair of shoes, I bought the latest in the series, the Guide 5. It is a great shoe, but I would caution those who have been using the Guide 4 shoe that you WILL notice the change in offset from 12 mm to 8 mm. I did almost immediately and initially it was uncomfortable. I got used to them after a few miles and I think in the long run I will be better off with them. However, I doubt I can use the 4's as a backup pair because I think it will be uncomfortable going back and forth between the two.

Update 9/27/2013: These shoes have been fantastic. I bought a 2nd pair without hesitation.