Twin tips are cool because;
They spew massive rooster tails
They look like snowboards
They turn like a shorter ski, but float like a longer one.
They suck because:
Noone lands backwards on them.
You need a good tail hook system to keep your skins on (clip-fix sux)
You can't stick them in the snowbank outside the hut.
And the pocket-rocket is a piece of poo, most fat skis today (twin tip or otherwise) perform better, and last longer than the pocket-rocket... hence the name, eh?