I use 4-12 for my rimfires and I basically never take it off 4x to shoot, I feel Spoiled to use the 4x.
The 12x to me is almost strictly a "spotting/scouting" feature, to see a little down the range/target area. I.e. sneaking and peeking on the target.
4X is basically cheating at my 25yd indoor range, up to 75 yd its good, at 100yd I might try dialing up some if I need it.
Just might want to look at this:
http://www.nikonhunting.com/spoton/
That is the best thing ever... I happen to have two Nikon ProStaff scopes but I am sure it would work for others: It shows you how to enter your scope info, enter your important bullet info (Say in my case, a 36 gr CCI Mini Mag) and how I'll be a 4x, shooting at 25yds and I want a 100yd zero. So it shows me, calculates, zero so my shots are shooting about one and a half inches high, and if I am that inch and a half high zeroed' at 25 yds, I'll be "spot on " at 100 yds. THIS IS SO AWESOME.
Then I can change to say a 40 gr Mini Mag ( the round nose vs. hollow point) or maybe Federal Bulk, and recalculate.
AWESOMENESS.