I was very lucky to find an original unmodified FX1 in almost perfect condition on craigslist a few years ago. It is hands down the most fun ski that I have ever ridden. I started on a 550 and also have a square nose superjet and the FX1 is unquestionably better than both of them. As others have said, they can be very challenging to ride but once you get some experience with it it doesn't feel squirly or unstable anymore. It's a very honest ski in the sense that it will do exactly what you tell it to do exactly when you tell it to do it. It has tons of power and it is very agile. I'm 6ft and 210lbs and my stock FX1 throws me around like a rag doll.
Yeah the 122mm pump definitely doesn't hook up as well as the 144 in my SJ, especially in rough water. However once you get the hang of it you learn to appreciate the mid range/top end that it gives. I think Yamaha claimed 55mph stock. I've never actually measured mine but I can tell you that if you pin the throttle wide open on flat water you had better be hanging on because it will go into warp speed in no time.
Be careful when jumping waves with it. It weighs practically nothing and it will come way higher out of the water than you might expect. I highly recommend a lightweight motocross helmet. Mine has definitely saved me from knocking myself out when it has gotten away from me in midair and I've come down hard on top of it.
If you ever come across an FX1 for sale don't hesitate to pick it up. Mine is one of the most fun toys that I have ever owned and I will never sell it!
