Should I move from Windows to the Mac for developing and testing my iPhone web app?

[ab5zn]

First let my ask this: Is there a good forum dedicated specifically to iPhone Web App Development?

I've been developing an iPhone web app on a Windows XP box using
MobiOne Test Center and Safari for testing and debugging and
occasionally using a real iPhone for testing. The problem is that
MobiOne, Safari (desktop), and the iPhone all produce different
errors. Obviously I am most concerned with the errors that occur on
the iPhone, since that is the target device. (An example of the type
of error encountered is that an image that ordinarily appears as
expected occasionally cannot be displayed, so the little question-mark
icon appears instead.)

I have the opportunity to obtain a Mac for development, but I need to
know whether using a Mac will make a difference.

• Have any of you moved to the Mac for developing or just testing a web-
  only iPhone app?
• Is doing so worthwhile? Why?
• Does the iPhone simulator in the SDK simulate an iPhone better than
  Safari on the Windows desktop?
• Is there a reason I would need a paid subscription to the Apple iOS
  Developer Program?

Thanks!