Hi devadiva,
No, I've never been a marine. I was in the army back in the 1980s-90s. The drill sergeants look (and sound) kinda the same. I prefer kinder, gentler exercise these days (like yoga) without all that shouting.
The Marine Corps Marathon is fun though. This will be my 4th. They really treat you well - especially considering there are so many people in it (30,000).