If I understand it correctly, the sender needs to have a Barclay's bank account. If the recipient doesn't bank at Barclay's then the recipient needs to link some other U.K. bank account and funds from each PingIT payment are transferred there (after a delay .. next day maybe?)
This is similar to Dwolla and PopMoney in the U.S., though the differences are with Dwolla funds need to be transferred in to Dwolla first, and with PopMoney the transactions much clear through ACH first (not instant).
This could be great for those wishing to do person-to-person, over the counter trading (such as on the #bitcoin-otc marketplace). What risks exist due to reversals though is yet to be determined.