Ordinarily a market comprised of a couple monolithic competitors really annoys me, but I do think this will ultimately be a boon to merchants. (Yet I am fascinated by Google, I know. [shrug])
One of the nice things about Amex is that everything is all handled by them. Amex holds the line of credit, administers the card, and processes the transactions. Yet it's more expensive for merchants to accept. If Visa is acquiring its own processor, this could potentially make transactions a lot easier to deal with for the merchant but at a much lower cost to them. Good move, Visa (assuming of course that CyberSource share holders will go for it).