Yes, it is. Purely because it is so popular and most people have a Paypal account, and also the process is so quick with Paypal that they don't have time to change their mind lol
Yes true, you can also pay with creditcard via paypal, so that's kinda cool too Paypal is the best option
Depending on how technical you want to get, PayPal has told me in the past that any income you get from "donations" is still taxable income unless the entity that you are accepting donations to is a properly registered 501(c)(3) entity (otherwise known as a non-profit corporation). Just purely an FYI, it may not really make much of a difference to you.