I guess the extra weight, complexity and cost kept me away. I was also concerned about the higher center of gravity. But, of course without riding the 260 iS, all I had to go on was the reviews I read and my dealer's recommendation (who knows if he had an iS in stock when he recommended the X??).
In any event, for most of my riding I think I'll be OK without the suspension. Most of the time I'm pulling a tube at low speeds or waiting for big waves to do some jumping. I also like cruising on quiet evenings when the lake is flat.
At my lake, there isn't really anywhere to travel to (i.e. I'm not on Lake of the Woods, MN where allot of people island hop and even camp out). I'm on a huge inland lake and we usually head out of he marina and stay within a few miles - riding back and forth. At times a bit boring, so I end up staying in unless it is a big wave day or it is flat so I can have some top speed fun.
I'm sure now that I have a new X, I'll get a chance (coincidentally) to try someone's iS (there is a Limited iS in the marina - which I understand has a softer suspension and seat than the iS 260). After that test ride, if I feel I'm really missing out, I'll trade.