I only saw Mosconi twice (in the early 60's post-Hustler boom). Unfortunately, he didn't run 100 either time - off days, I guess. But I remember a couple of things about his play that surprised me. First, he was fast. He never took time to think, he just did it. Two quick practice swings, pocket the ball, and charge off to the next shot.
Second, his break shots were amazing. The cue ball didn't seem to pop open the rack, it plowed through it like Dick Butkus against high school linemen. The guy had one powerful stroke. I remember going back to the poolroom and trying to make my cueball act like that - never could.
As for the record, damn, I hope nobody ever breaks it. Not because I worship Mosconi, but because, as sure as night follows day, whoever breaks it will be acclaimed by many to be the now indisputably greatest straight pool player of all time. And that would be wrong. Running 526 doesn't make Mosconi the greatest, his many years of dominance against top competition does.
I like Irving Crane's quote regarding Mosconi - something like "I can do everything on a pool table that he can, so why can't I beat him?"
If Babe Cranfield, who ran more than 700 in practice, had done more exhibitions and tried hard to break Mosconi's record, he might well have broken it in front of witnesses. But what would that have proved? He never beat Mosconi in the tournaments.