It doesn't take an expert to demo skis. In fact, I'd suggest that everyone give it a try.
I personally tried all different types of skis from Cole Sport the second year I was skiing, as a green/blue skier. This on-mountain approach allowed me to try each ski back-to-back on the same run to really feel the subtle differences. It might even change how you ski your favorite runs, be it trees, groomers, bumps or steeps.
It taught me so much. There are different types of skiing that come from different types of skis. For example, after that year, I was all about carving skis. Now, though I use my fat powder/all mountain skis more often.
I'm not an expert, but the guys that are can tell you much more about just what type of ski is perfect for what type of skier you are. You might have a favorite brand, or favorite type, or style, but I challenge you to think outside the box. Being a creature of habit might make you miss out on a great ski.
I took a local that'd been skiing the same ski for longer than I've been alive and forced him on to a pair of S7s. Blew him away.
Basically the lesson I learned and want to share is you may THINK you know, but you might not know. The game is always changing, and while buying the newest technology each year might be excessive, enjoying a day testing it out can be a blast.