Almost every time I fly with another pilot they point out something I could do better. I've done it to them a fair number of times too. We all learn and benefit from this, and the ability to exchange such points in both directions is essential to a competent aviator.
It should be said though, that of all the sins I've observed, a failure to do a proper DI and pre-flight checks is far and away the second most common. The most common is the failure to do a pre-take-off crew & pax briefing.
Genghis
Who is not claiming perfection either.
[This message has been edited by Genghis the Engineer (edited 11 February 2001).]