I'm a fan of the "1500 hour rule' because it raises the bar to applicants, thus narrowing the field of available pilots and making us a more valuable commodity. It's interesting that doctors have been mentioned, since the AMA has been doing this for years by controlling medical school admissions.
As for the Colgan tragedy, some of you are talking like the CA went straight from a Seminole to the left seat of a Q400. He had airline experience as both a Captain and First Officer. The problem was fatigue among both pilots due to improper commuting which led to poor judgement and mistakes by BOTH of them. Yes, more experience may have helped, but when people commute on a redeye, sleep in crew lounges, then fly all day, it doesn't matter how many hours you have, you're going to screw up. So the "1500 hour rule" IMO adds little to safety, it was a convenient excuse to raise the bar.
As a side note, we have had many 1500 hour applicants recently struggling through training where 300 hour ERAU wonders used to make it through with no problems. Hours aren't everything.