Replying to Symmetric twin tips for all-mountian skiing???

I've been renting twin tip demos and love 'em. Don't spend much time in the park but am interested in learning some stuff. I love to ski backwards, so I like the idea of a symmetric ski. But people keep telling me they're better used as park skis. Would I have problems on all-mountain terrain with symmetric skis? I do spend a lot of time on groomed runs, occasionally in the trees or deep powder too.

Anyone have any specific experience with any of these skis or other twin tips, skiing all-mountain and/or in the park, I'd love to hear your thoughts.
Line Anthem
Line Invader
Volkl Wall
Volkl Ledge
K2 Extreme