I took a course from Bill Dvorak at his rafting outfit in Buena Vista. The class was really good, but mostly focused on rescue from a rafting perspective. He's definitely got a lot of experience and that comes through in his course.
I also know that BOC and several other denver area places offer classes. Some classes offer an actual certification, which may interest you if you're going to work as a raft guide, safety boater, etc. The certification does not necessarily mean its the best class for kayakers to take though. Look for a class taught by someone who has a lot of experience in the kind of boating you do - rafting, class V kayaking, etc. You also probably want to make sure that the instructor has a certification to teach ww rescue.
As for the rescue vest, I believe that it is an important tool, but by no means do you need one to take a class. Chances are that someone in your class will have one and it's good to understand how they work and their limitations.
Also, make your friends take the class with you. After all, it's not their lives they'll be saving....it's yours.