I like using the 60 when I need to get the ball up quickly or don't have much green to work with.
The other time I like it is in the bunkers that are really dirt instead of sand. If I open up my 56, the club with the most bounce, it will tend to not dig into the dirt and skip into the ball...leading edge first!
I use my 58 and 54 for green side bunkers.90% of green side bunker play is 10 yards. So which wedge do you use ? If the ball is on the uphill slope with a decent lie I will use the 54. In this same scenario if the pin was 3 to 5 yards from the ball I would use the 58. For a normal flat lie to a typical 10 yard pin I use the 54. I may use the 58 if the front lip is high. For a ball at the back of the bunker on a down hill slope, you are screwed. You just need to get out and the ball is not going to check up but run. If the distance from the back to the front is more than 7 - 10 yards I will use the 54. On green side bunker play where the green slopes away downhill I will use the 58. For plugged lies in the front slope/lip I will use the 58 and just leave the club face burried like a hatchet. Sorry for the long response but the bottom line i use both the 54 and 58 depending on the lie. Of course for pins over 10 yards away which would fall in the 10% range the 54 or even my AW or PW may be the club of choice. For rain hard packed sand you can't get your normal 58 or 54 to slide under the ball using the bounce because you will end up just letting the leading edge bounce into the ball and air mailing it over the green. Use your AW or PW with e V type swing and just get it our.
I use my 56 out of any sand. I have a 60 in the bag but rarely use it becasue I haven't given myself any practice time with it. I like what some of the posts said and will be working on the 60 degree to use in some of the situations that were brought up on the thread.