You should use it at least once. If you've never used a super speed before, you'll be in for a pleasant surprise. They are nice shavers. I like them with Astra SP's, though feathers work well in them too.
Speaking of my father's old razor, no, I do not have it, but I remember something about it. His brother-in-law was some kind of salesman and he only used the Gillette blue blades once or twice to get a really close shave. He would bundle them up once in a while and send them to my father who would then use them for a while. My father was a butcher and had to always wear a long sleeve white shirt and be clean shaven. I had forgotten about that until you mentioned about not having your father's razor.
Earlier in my shaving journey I had this problem with ultra-mild razors. Somehow I was expecting a certain blade feel and as a mild razor does not give it, I added some pressure without noticing it. Could this be a problem for you? Then there is another thing with iKon X3: the blade alignment. It does not align the blade automatically correct. After popping in a blade, I am lightly squeezing together the head with my fingers. When looking from above down on the top cap having one of the short sides towards myself, I push in the lower right corner and the upper left corner of the blade with the handle. Those two corners are almost always too far out and using the handle as a tool for aligning the blade is more safe than using my fingers. After this I attach the handle. iKon X3 is almost the only razor I use nowadays and sometimes one of my kids has been sneaking into the bathroom and in secret shaved with X3 and he too finds it very smooth.
I have noticed that the Ikon X3 is very hard to align the blade. I always seem to have more sticking out on one end than the other. I'll try pushing the blade around with either the handle or an old fashioned lead pencil. Thanks for the suggestion.
I just used my father-in-laws razor with a new Shark blade. It seemed to be very harsh, but gave a close shave. I have noticed even with my Astras in a razor that they seem to get smoother after a shave or two.
Good stuff but it works even better to palm strop a de blade while still in the razor so it stays stiff, just loosen up the cap for it to make better contact plus you can use the cap as a guide to keep the angle constant. TTO razors are the easiest to do this with just unlock enough to take the bend out of the blade and that should be good enough. The technique(s) are straight forward try to use a down or up stroke (whatever is more comfortable) holding the handle perpendicular to the ground and adjust your palm until the feel is correct. The other way is to hold your palm perpendicular to the ground and find the angle that way with an up or down stroke. It is pretty much fool proof once you get the feel portion down and find what is most comfortable. This is also one way to get a feel for a razor's mildness/aggressiveness without using a feeler gauge by doing it with the cap fully locked down.