Recently bought a pair of Zag Big 178's (January '08). Had not tested them but a ski instructor I know raved about them.
I have been skiing for twenty years and try to ski four weeks a year. I have been through bandits and Dynastar Legend 8000's. Ultimately found the bandits to be too soft. I like the Legends but wanted something to open off piste up for me even more and allow me to still enjoy carving. (I know I should probably have more than one pair but wife and two kids to support).
Considered all sorts including Mythic Legends but ironically the Zags were available in West London but the Mythics were not.
The ski's have delivered on both counts. The 138 tips are flexible and float easily in powder and they are surprisingly quick edge to edge on groomed piste with a turning radius of 13.5 meters. They are very stable at speed.
As long as you shift your weight slightly back they handle easily in crud. Putting your weight slighly back on the heel and drawing it in gives an easy quick turn in all sorts of rubbish.
They do not like ice.
Interestingly you tend to get raised eyebrows from ski professionals when the see the Zags, and while none are too specific about their reservations I suspect that soft tips and the slight adjustment to skiing style goes against the grain for some of them.