Recently I've noticed a lot of arguments online about "prog rock". Its getting a bit crazy.
The argument goes like this:
"Prog Rock" is genre that existed in the 1970's and was played by the likes of King Crimson, Yes, Genesis Etc. There can be no more because it only existed in the 1970s. Some prog zealots accept the later "neo-prog" movement Marillion, IQ, Etc. These guys are generally very angry and don't want the term "prog" associated with anything later - even for example Porcupine Tree. (yes prog is a genre where some fans are actively against progression!)
"Progressive Rock" is a bit more interesting. My definition of this is "interesting and ambitious rock music". It goes from King Crimson to Mahavishnu Orchestra to Can to Talking Heads and Dead Kennedys to Radiohead and Cardiacs, Mars Volta, Tortoise and Battles.
None of those terms really matter.
Its probably best to just enjoy the music - although its odd some fans of "Progressive" music hate progression and want "prog" to die when the old bands do. Very weird.
BTW - I know my music isn't proper "prog". I'm not sure what it is.