Yes it is secure and on their site, you can give your credit card information. But beware of spoof emails that look like paypal
I have blogged about a spoof mail that I got.
Paypal has various accounts. Read thru their Knowledgebase for more information. I am using a merchant account so that I can also received Credit Card payment
Question 2:
Its vert clearly mentioned in their Knowledgebase. Please read it.
Question 3:
It depends. For some its nice, for some it isn't. Have a look at *www.paypalsucks.com