It is absolutely free, but there is a fee for dormancy.

Virtually anyone. Excluded merchants are governmental agencies (including but not limited to federal, state and local taxing authorities), collection agencies, as well as the recipients of court-ordered payments such as child support and alimony. Payments to any persons or organizations outside the US are also excluded.

Absolutely. Once you add your payees (name, address, phone number) it's so easy to use, you'll never want to do it any other way. Plus, you save on stamps and time.