Hey, I know the guy in that video
Oscar,
I have the Raymarine S1 which I guess was replaced by the X series you're considering. Only diff is probably a smarter computer. I read from other owners that responsiveness under power is not good. That is not my experience. The pilot does an excellent job under sail and power. It only doesn't work well when motoring slow without fins down, but same can be said steering manually. The trick is proper installation and setup. There are many computer settings and tweaks. I'm a tweaker

so after various configs, I think I got it just right. It also works better with gps connect via nmea or seatalk. This way the computer can read not only the heading via its electric compass but the actual course from gps, using both pieces of info for steering accuracy. I installed everything myself. The tricky parts are the rudder sensor and bracke for the back side of the wheel drive. This may be most challanging for the new pedestal style (07 M or newer.) Mine is an 05, so I didn't have this to contend with.
I am very happy with the unit, and believe me, I put it through plenty. Number of videos posted on this site with Rusalka's AP doing its job, and doing it well. I would also recommend getting an ST40 wind system... I believe you can get them for a song now days. This unit can interface with the AP and steer to the wind i.e. lock in a wind angle and the pilot follows it. Nice way to take a break from sheeting the sails. I also enjoy seeing exact wind velocity and direction.
PM me if I can answer any specific questions.
Cheers,
Leon