How Do You Rate "Which Teacher's Worth More Money?"

Should good teachers make more than bad ones?
The Obama administration says the nation needs to start rewarding merit, and economist Michael Podgursky of the University of Missouri agrees. It's just that there's no simple means of carrying that out.
Yesterday, NPR's planet Money program discussed Which Teacher's Worth More Money?  This story posed many interesting educational "riddles" from how do you attract, hire and keep qualified teachers to how do we ensure that colleges are producing qualified, well-trained teacher candidates?
Currently, the most pressing question due to national attention and potential reform is how should teachers be paid?  As a former teacher, I cannot agree with a system that is solely based on performance simply because there are an incredible number of factors- not controllable by a teacher- that affect student performance.  At best, I could support a form of merit pay based on student, class or school improvement.
What I appreciate about NPR's discussion of the topic is their angle of what if everyone's jobs were merit based?  What do you think your co-workers, your boss, your car mechanic, your doctor (the list could go on & on) should be paid?  If this system of compensation makes sense for teachers, then why not have it for everybody?
Weigh in on the through to the story then share your opinion or experiences!