Personally I mount everything true center, and I always have to go to the back of the shop with a tape measure to be sure they don't fuck it up.
My reasoning is that I like skiing backwards when I ski. Having a ski that isn't absolute dead true center doesn't affect you much for jumping, rails, tricks, etc - but I do find it makes a big difference if you really want to haul ass going switch down the hill.
The only catch is that you lose some forwards performance in order to get that switch performance. Center mounted park skis in either deep snow, moguls or trees make you hate your life.
If you want to enjoy dead center give up on moguls, and be sure to have super fat skis to rock trees / pow.
Skiing backwards 50% of your day is a riot.