Matt, I agree with your points 1,3,4,5,&6. As for Point 2, since image is important in today's market, it does benefit a performer to belong to a PRO. Which unknown artist with great songs would be more impressive to a music supervisor, producer, or A&R guy - the one with BMI on his business card or the one without a PRO? Since the competition is so tight, any little advantage helps and joining a PRO is not expensive enough to make it cost prohibited.