@ChrisMartin. The google service you are looking at it appears to be if you wish accept credit cards as part of an e-commerce website. The service I am describing is for peer to peer payments. When the sender sends from either their bank account or "Google Wallet" balance the transaction is free, If the sender wishes to send from their credit/debit card then THEY will incur a fee of 2.9%, with a minimum fee of $0.30. Either way it should not affect the amount of money going into your account.
https://wallet.google.com/termsOfService?type=BUYER&gl=US
6.6 Fees
GPC may charge fees in accordance with the then-current fee schedule, as stated herein. Google Wallet may assess a fee of 2.9%, with a minimum fee of $0.30, per P2P Payment charged to the Sender for P2P Payments processed through the Service. Such fee shall be waived where your Google Wallet Balance is used for the P2P Payment, or an ACH-enabled checking or savings account is the Funding Account for the P2P Payment.
http://www.google.com/wallet/faq.html#tab=faq-fees
Sending money
Google Wallet Balance: No fee
Bank account: No fee
Credit or debit cards: 2.9% per transaction (minimum $0.30)
Receiving money
Receiving money: No fee
