A short anecdote on the subject of 1stSgt vs Master Sgt, etc -
Our company 1sgt that joined our infantry company just before my last deployment (back in '97-'98) had spent his entire career up to that point in supply, but wanted to retire as a First Sgt rather than as a Master Sgt, so he managed to get some strings pulled and got sent to an infantry company. Now, he was a nice enough guy, and you gotta respect him for, at his age, trying to do what us young 03's had been doing for awhile - it took some balls and he showed he had some serious heart, but he had a hell of a time with the physical side of the workup - the hikes, the runs, the long weeks out in the field - and most entertaining were the rides in the helos or fastboats. He would prone out on the floor of the birds or the kodiaks with his face buried in his Kevlar to attempt to hide his puking, and holding on for dear life to the corners of the ride!
It was a little tough to keep motivation up among the company when the 1stSgt, whose supposed to be leading the hike is falling back. The NCO's and senior NCO's would help try to play it off like he was going back to check the lines - whatever worked.
The old guy toughed it out and made it through the training and our deployment, and was able to retire with the feather in his cap of having run an infantry company. Like I said, gotta give him credit, he stuck it out even though he was way out of his element at first, and not physically up to par - but he kept at it. Couldn't have been easy - he was pushing 50, and had spent the vast majority of his career handing out uniforms and maybe doing minimal PT, then thrust into our circumstance, with a bunch of 20-year-old (and younger) kids who were gung ho and had been doing the really hard PT and long steep hikes and runs almost daily for years.
Anyways, it's a big deal to retire on the 1stSgt side of things rather than Master Sgt. Not to demean the Master Sgt side either - I knew a seriously tough and grungy Master Gunnery Sgt who was tough as nails!