Pc1 and Limpinhitter:
There's no question that the pro majors were significant tournaments, or that the pros were better than the amateurs. There's also no question that it was a very impressive feat for Laver to sweep those tournaments in 1967. The 1950s and 1960s produced fantastic tennis: I view Laver and Pancho as two of the greatest three players of the past 80 years.
But I started this thread to disagree with what I see a lot in this forum, which is the claim that pro majors were basically like starting a modern Slam in the quarters, with the top eight players. They most certainly were not like that. Just look at Laver's draws in 1967: he won 13 total matches to sweep the pro majors, and 5 of those matches were against guys who definitely weren't top-10 players in the world (most not even close), with another 3 matches against a guy who wasn't in the top 5. Of the five matches he did play against the best competition, three were against Gimeno, who is an analogue to Andy Murray: excellent, but never a guy who really challenged for #1 or won majors (excepting the 1972 FO over Proisy).
Still, it's a great feat. But not that great. Rosewall basically duplicated it in 1963, and Pancho would have done the same in the mid-1950s if the French Pro had been played on indoor wood (or maybe just played at all) then. It's no stretch to imagine Federer, Nadal, or Djokovic doing something like that at their respective peaks.
What no one else did, by contrast, is win the Grand Slam like Laver did in 1969. That was a much, much more important and difficult accomplishment.