In The Cathedral and the Bazaar Eric Raymond said "Given enough eyeballs, all bugs are shallow." The phrase, he calls Linus' Law after Linus Torvolds, is probably one of the most memorable and most repeated phrases (in one form or another) from the essay.

This morning I read a post on The Open Road about new data that supports the anecdote. Matt quotes from the CIO Magazine post:

According to a survey commmissioned by BMC and conducted by Forrester analyst Carey Schwaber, the average time to resolve an application problem is 6.9 days for enterprise developers and 6.7 days for software vendors. Ten percent of those problems take 10 days to solve, says the report. Developers spend just over an hour documenting the problem; and, if given that hour back, they'd use it to create enhancements to the application they are working on....

...Evans Data Corporation (EDC) just finished its twice-yearly report, resulting from a survey of several hundred open-source and Linux developers (with some managers, but primarily folks-who-code). The EDC numbers are somewhat different. The average time between discovery and solution of a serious bug, for 36 percent of open-source developers is under 8 hours. Hours. Not days. Not a week.

Of course, as Matt notes, it's not that all open source software is better, but that open source lays the foundation for "better." My own experience certainly backs this up.