The only times in my experience that I had to think about an ability estimate was when I as an inexperienced ski shopper had to go shopping for skis, when I requested a lesson, and when I had to fill out some form for ski patrol.
I did notice though, some few decades ago, that if I identified myself as "expert" when demonstrating for potential purchase or just renting skis, the ski shop people were more likely to offer me skis that I liked.
Speaking of experience, there in lies one of the roots as to what makes someone like one ski vs another, that and what you intend to do with the ski.
On my first ski shopping trip, my experience consisted of having skied on very long WWII surplus skis that my dad found on sale at the Sally Ann. I did not know much about skis, only that the skis I had been on were a big trade-off between high-speed stability and maneuverability. As I knew that I liked to ski fast, but was a relative newcomer to the sport, the salesman set me up with a pair of 180 cm GS skis (I weighed about a buck ten), they might even have been junior gs skis. They had fiberglass! They felt so smooth compared to the old long wooden skis. I enjoyed that smooth fibre-glass feeling. They were not stable at high speeds, even the relatively low high speeds I was able to reach on my local 700' hill. I did not enjoy the feeling that they might rattle off my boots at some inopportune time. Maybe it was poor technique. I, being stubborn and not financially well off, made do, although I did enjoy renting the latest greatest every now and then.
Many years later I could afford a top-level ski, and decided to buy a pair. Since I was still a speed daemon, and my experience included skiing too fast on unstable skis I narrowed down my search using magazine reviews for those skis that were stable at speed. I demoed many skis and settled on the Kastle SGs. I did enjoy the quickness of the Dynastar SLs, but they were not stable at speed. The Dynastar GS of the day (chicken hearts) were better, but not better enough and they didn't have the quickness of the SL to compensate. I wasn't impressed enough by the Rossis (7S 4S K ? VAS damping - liked the Dynastar SLs better). Fischer RC4 GS came close in terms of stability, but not close enough.
Many years later, shopping for shaped skis. Tried out a whole bunch. Had enough experience to like both the heavy solid felling of the Atomic SX11 and the quick as thought and lightness of the Solomon Equipe 10 Pilots. Ended up with something in between.
Edited by Ghost - 9/9/15 at 12:18pm