Head XP100Me: 20+ years skiing, double-black freeskiing skills (Whistlerites: Spanky's, Pakalolo, The Couloir). Tall, about 180 pounds.
Current favorite ski: Volkl G41
Setup: Head XP100 Cyber 170cm, Tyrolia rental binding
Conditions: Varied. 10" of cut-up pow, crud, groomed, moguls.
Head advertises the XP100 as a high expert all-mountain ski biased towards hard conditions.
Looks: They look butt-ugly in pictures, and in person they're only marginally less ugly. The solid black resolves into a very, very deep purple with a subtle carbon-fiber waffle pattern, but their short length and extreme sidecut (122-67-108) still make them look like evil clown shoes. All my skis are butt-ugly (brown Snow Rangers and so on) so I don't mind.
Weight: Jesus, these things weigh. Maybe it's the Tyrolia rental binders or the built-in riser plate, but they still weigh a ton more than my 188cm G41 + Salomon 912. I had to keep switching shoulders on the walk from my car.
Stiffness: Very stiff. Right up there with Head's slalom racer or my G41s.
OK, now for the skiing part. I'll split this up, since the ski has two completely different personalities depending on snow hardness.
They're great in pow up to your boot cuffs, but anything deeper causes them to sink due to the narrow waist (67mm) and stiffness.
They have great crud and chop manners since they're so stiff. Just blast on through and make any turn you like. The huge sidecut doesn't hang up in soft snow.
On groomers or hard snow, WATCH OUT. These are the only skis I've found that can run away from me in half a turn. Just tip them on edge and you feel like you've been shot out of a cannon. That 12 meter sidecut kicks in, and nothing will shake it loose; not crud, little choppy bumps, ice, bricks, or anything else. You will rail your carve until you decide to roll your knees to the other side, at which point you whip around like some sort of demented carnival ride and do it again. They will hold any carve your legs can.
I spent the first three runs getting thrown into the backseat every other turn...fortunately the sidecut is so extreme that you carve even leaning back. Roll your knees while exerting shin pressure and you'll think you're on a new-school race slalom.
The tough part: these skis are nearly impossible to skid or hard snow. You can initiate a skid turn, but once the edges bite they will not let go, ever. And they really want to bite. So you will rapidly find yourself going 600 MPH on anything steeper than a green circle, because pure carves don't scrub speed.
It wasn't as bad as I thought in moguls: the short 170cm length made up for the stiffness and wide tip.
It skis very long: at no time did I feel like 170cm was unstable or too short, even though I normally ski a 190.
Verdict: The head XP100 is the best pure carving ski I've ever tried. However, it requires superhuman strength and stamina: I am in great shape from regular cycling and skiing and this ski completely kicked my butt. At the end of the day I could hardly walk.
If you want to experience incredibly brutal G-forces on a regular basis, this is your ski. I think of it as a race slalom widened up enough to handle crud and minor pow, and as such, highly recommend the shorter lengths. I can't imagine anyone short of FIS GS racers skiing the 184.