theres a lot of threads on this if you search it...
But if you do a lot of all mountain skiing, mounting at recommended (or atleast back from center) is probably the way to go because the shape of the edge allows you to make a better carve. You can still carve a center mounted ski, it just doesn't hold an edge as well. the side cut of most skis arent made for them to be center mounted so when you do mount them there you can still carve but not as well.
If you spend a ton of time in the park and carve switch, or if you like to carve switch all around the mountain then center mounting or close to center is probably the way to go.
some skis it doesnt matter if you center mount though, there are some that are meant to be center mounted like the addicts and invaders.
he got it spot on, if your ski is not designed for it then your just fighting its flex pattern and all the fun stuff. As far as turning is concerned, i found it made the turn radius shorter and my skis felt alot peppier. I say do it its way more fun. My skis are public enemeys and the core center is stupidly far back but that didnt hurt the preformance.