From my experience, its not "Flash" that draws conversions, its interactivity. Just doing the equivalent of an animated gif with flash is not going to get you very far and won't be worth the added expense.
Cool animation and motion does draw the eye, but in order to break out of the 'banner==ignore' training that everyone on the web has undergone, the ad needs to react to the user. Responsive sound, responsive animation, further information, etc etc.
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Check my sig for fast loading responsive shit thats not in flash
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