So this has churned around in my head for a while. A year or two ago when the endless question of which ski to purchase came up, I recommended against demoing and just buying a pair of skis. A poster flamed me as saying that was the worse advice ever given on this board. IMHO demoing has little value. If we could demo boots that would be another matter, but we can't.
Before I begin there are some times where I think demoing skis is worthwhile. You have a shop you want to work with and they will give you the cost of demoing back towards the purchase of a new pair of skis. You have a season pass at a mountain and ski the same trails all the time; might just as well change it up when the demo day is in town. You want to try something really different-full reverse camber, 5 point radius, carbon skis, etc..
Reasons not to demo:
1) Costs money if you demo through a shop.
2) Costs time on the hill if you go to a demo day. If you are looking to buy powder skis, conditions rarely allow you to test them in their element.
3) Usually limited selection of skis to demo
4) Factors such as tune and mount point have a significant impact on ski feel. With the demo you get what you get.
5) Psychological and physical state impact your response to the skis when you demo-we all have good/bad runs/days. Ideally a demo would allow you to ski the ski for several days. Comparing skis would take quite a while.
6) Drives you to purchase the newer more expensive skis.
7) Best prices are in summer when it is impossible to demo.
Here is my story on why not to demo skis. A number of years ago I had my first quiver of skis. My fat skis were Volant FB and I had picked up a pair of Atomic SX11. I was in SLC with friends skiing the mountains and at the end of the fourth day my legs were tired from skiing the heavy Fat Bastards. There was no new snow so I mounted the Atomics. The next day I felt like Tigger. I was jumping off everything. The skis felt so light and responsive and they could lay down railroad tracks everywhere. I thought they were the best skis ever and if I had demoed them I definitely would have wanted to buy them. Over time I came to dislike the skis and eventually sold them.
What is my advice? Buy the ski magazines equipment issues or look online at past issues-have not searched, but assume they are archived. Read their descriptions of types of skiers and the types of skis aimed at them. Decide who you are. Buy past years models of the skis aimed at how you ski through your venue of choice-online, tent sales, old stock in shops. It is not hard to get 50% off. Almost all skis are good nowadays at meeting their target. Buy bindings that put you not at the very end of their din range (you can easily see what your din range is online from a google search) that fit your budget-bindings don't matter too much unless you are sensitive to ramp angles. Shops will mount the bindings for a fee and they are happy for the income and you are happy for the savings. If after a while of skiing them and accounting for factors such as mount point and tune the skis are not for you, then you can sell at not too much of a loss and repeat. Really you would likely be at the same point if you had demoed and bought skis except it would have cost you a great deal more money.