I've integrated about half a dozen e-payment gateways, from popular ones (like paypal) to not-so popular ones. It seems every time I try to integrate a non-popular epayment gateway, I exceed my original time-estimation. I think I'm a decent programmer, but my time estimations probably needs work. Do other programmers run into many "surprises" when integrating e-payment gateways they've never heard of? Any advice will help. thanks