Yesterday I had a pretty good gut check. A 12 mile road march with a 40 pound ruck (not counting web kit, rifle, helmet and water) to be completed in under 3 hours. It was different from the last
gut check and probably more of a mental challenge than a physical one.
The RPAT was by far a more complete physical assessment. It certainly isn't easy but no matter how much 'guts' you have unless you are fairly strong you aren't going to get up a rope with heavy body armor on. Either you have been putting in the time at the weight pile (or just have the strength) to get your butt up the rope or you don't.
However with a road march it is a lot less physically demanding and a lot more guts. Not to say it isn't easy or that it will not kick your butt but that it is doable. Of course if you haven't gone on a hike or a run in decades or your feet aren't conditions to walking in boots with a load it isn't going to be pretty. However for someone in reasonable condition with tough (conditioned might be a better word) feet road marches are doable. They can be gutted through if you really want it, unlike the RPAT where all the guts in the world will not get you up the darn rope with an IBA on.
They are not very hard but they are not very hard for a pretty long time. A guy who is a total beast (the sort of guy who does iron man's and spends his whole weekend running and working out instead of sleeping in and relaxing) can do it in about 2:25 which is still a long time to push yourself but for the rest of us folks a time between 2:45 and 2:59 is more typical. Some of those lanky 6'3" guys can just stride it out but the rest of us have to run a significant part of it. Those folks in the 5'5" and below group have to run a lot. A couple guys came in and promptly passed out. Their physical condition might not be ideal but they certainly passed the gut check.
Gut checks suck because well they are hard and stuff. However it is impossible to ignore the fact that most real survival situations would be a serious gut check, maybe physical and maybe not but certainly not fun. Also it is probably a valuable thing to know what you are really made of.