>What do you guys think of having the component manufacturer source the parts?

I'm assuming you're asking about having the contract manufacturer source the parts, right? This is typically called "turnkey" contract manufacturing as opposed to "consignment" where you source the parts yourself. It really depends on the kind of product you're building and your ability to negotiate with component distributors an manufacturers. If it's your first time around and you're optimizing for speed, turnkey is probably the way to go. If you need specialty parts and you know how to source them more effectively than your CM, then consignment may make more sense.