@zerazid:
Not exactly sure what you mean. Are you asked for payment details on Paypals page or still on FastSpring?
If on Paypal: You are probably looking at the options for users without a Paypal account, there should be a login-option for existing users somewhere on the page. You should not need to enter your details on the Paypal page.
On FastSpring: Afaik, all merchants are required to keep track of basic customer data for invoicing. I believe merchants can get the billing/invoice information directly from Paypal though, in that case customers don't need to enter the data separately. I am not exactly sure why FastSpring is not doing that, but i would suspect it is because they offer various payment options and prefer to use the same input forms for all of the options. I can forward the question to them if you are interested in a definite answer.
@Qubie:
Sorry for the late reply, i somehow missed your question.
The two most interesting plots are probably:
1) The "Best Response" plot can help you with problems like:
* How does your best response range change depending on an opponents range?
* With varying opponents range, what is the equity difference between your current range and your best response range?
* Against an opponent playing best response against you, what is the most profitable range for you to pick? (Note that the answer is frequently NOT the equilibrium range, unless we are in a ChipEV situation.)
2) The "Hand Equity" (currently in the Beta version) plot shows you how the equity of individual hands changes depending on an opponents range.
This can be useful if you want to determine how loose/tight an opponents range needs to be, in order for your hand to be profitable.