I checked out the site, seems really nice. I think the payer would have to register yes? Another question, I do have a PNB account (their trusted local partner) but do not have netbanking activated for it. Do they allow transfer to other banks say SBI. Also have you personally used this?
Payer does not have to register. The money is just deposited into their accounts, though it could take upto a week especially if you pay using your bank acct and not credit card.
There should be a list of banks they accept. It's pretty comprehensive I think.