I find them usually entertaining, sometimes irritating, occasionally educational, almost always enlightening:
Entertaining to see how people will express themselves, how they describe their positions or beliefs.
Irritating to see the occasional input of those who are so intolerant of beliefs that don't match their own.
Educational when I learn more about a culture, religion or philosophy.
Enlightening when they provide a reflection of myself that teaches me about myself, whether good or bad.