I agree with most everybody. I think that in the begining it is polite for the guy to pay but after a while the girl needs to pitch in as well. My bf and I have a mini-system where he still pays a lot but, whenever I can, I pay for big things (baseball games) or we even split it, like if we are going to dinner and a movie I'll pay for dinner and he'll pay for the miovie.
If the girl insists on paying you could either pull the line, "Next time you could pay" or you could just let her pay. Sometimes the girl likes it when the guy makes a genuine offer to pay for the date. PiKA2001, you seem like a great guy

P.S. about the whole guy friend paying thing, I have lots of guy friends and they pay for dinner or lunch when we go out, but we alternate now, because I feel bad for them paying whenever we go out.