I wholeheartedly echo all of the above. When I was at USNA, people often asked me that question. I responded that we absolutely had fun, but that our definition of "fun" probably differed from that of most college students. For example, getting swim call on "Hell Night" was totally fun (seriously).
If your idea of fun is going to frat parties, going into town during the week, dating whomever and whenever you want, getting drunk, wearing jeans to class, experimenting with MJ on occasion . . . then a SA isn't going to be your cup of tea.
I don't know that you have to have a twisted sense of humor . . . rather, the notion of "fun" changes based on your circumstances.
I do still vividly recall a mini-reunion of my (albeit small) h.s. class during winter holiday of my plebe year. I listened to what my classmates had done / were doing (taking 12 semester hours and being overwhelmed; going to frat / sorority parties, getting drunk (18 was legal drinking age then)) . . . and just shaking my head at what I'd accomplished in that same time.
I'd learned to sail, qualified in pistol and rifle, was taking 21 credit hours (that's what plebes did at the time), was in great shape, had learned to wear a uniform properly, could do great chow calls
, had learned to march in parades . . . I felt that I had already accomplished so much in such a short time that the things I'd missed paled in comparison.
During 3/C summer cruise, I sailed a 100' double masted yacht in the Caribbean. I remember having lookout watch, sitting at the tip of the bow with my legs dangling between the stanchions and thinking to myself: "I can't believe they're paying me to do this."
Being honest, you do give up certain elements of "fun" when you choose to attend a SA. That's why the SA life definitely isn't for everyone. However, those who stick it out would almost certainly say they would willingly trade their experiences for traditional fun.