You've gotten some good feedback here. Like many have said, it depends on what you want with the gun.
Personally, I was SURE I needed something in the 6-24 range for my .308 Rem 700. I ended up with a 4-16 Vortex Viper PST since it was what the dealer that I had hooks ups with had in stock and I didn't want to wait. Anyways, I've found that it was about perfect for me and what I wanted. At the time, it was learning about precision shooting, trying to improve and see what I can do grouping wise at 100 yards and to have fun hitting all of the stuff that used to be available to shoot beyond the berm at Koko Head. That's all gone now, but what I found was that the 16 power was plenty for me to shoot groups at 100 yards. I had a few chances to shoot the gun in the 400-600 yard range, but that was to hit larger steel targets and the 4-16 was plenty. I had planned on taking the gun out to one of the Puuloa shoots, but never did get around to it.
When I was looking at rifle scopes, I was also warned that clarity can be as big a factor as power. I'm no gear snob. While I've always wanted a scope with the NF, S&M, USO, etc name on it, I've been happy with my Vortex. That said, I've looked through some quality glass and was amazed at differences.