I've seen several, and participated in several when in high school. Was in the pit orchestra for South Pacific, King and I, and Oklahoma. Watched my brother as one of the boys in the local band in "The Music Man" (community theater production). Other high school productions I've seen are Fiddler on the Roof, Sound of Music and Finnian's Rainbow.
I saw a college production of Joseph and the Technicolor Dreamcoat.
The only professional production I've seen live is Les Miserables. I did see a DVD of the 25th anniversary live performance of Phantom of the Opera (got it for my niece who was a big Phantom fan at the time).