[sunir]

If you want another perspective on this, we have to answer these kinds of questions a trillion times a week at FreshBooks. We're posting a guide to help people get through it.

The most salient post is Part II, which helps people choose their gateways.

http://www.freshbooks.com/blog/2010/04/30/part-2-how-do-paym...

Speaking as someone who frequently has to call into the payment gateways' customer support on behalf of our customers who have hit a brick wall, personally, I like to keep life easy. I recommend PayPal Standard if you're doing less than $2000-$5000 a month in transactions, and then Authorize.net or PayPal Payflow Pro.

[bvi]

How easy/painful would it be to switch from PayPal Standard to Authorize.Net or PayPal Payflow Pro, if the situation arises?

[sunir]

Moving from PayPal Standard to anything is pretty easy since for most people it's a very simple payment service.

The other gateways are more complex since you cannot migrate the credit cards, and if you have recurring profiles managed on the gateway, you will have a harder time moving as you'll have to convince your customers to punch in their credit card again.

[ovi256]

>you'll have to convince your customers to punch in their credit card again.

Give them a free month, or 5 free GB, or what have you.