I agree, the only way to "truly" inspect a QFN is with an X-ray. But this might be over-kill for him. He asked about soldering, not inspection. We use QFN's regularly and you can inspect these parts from the side to see if they are soldered. Unfortunately, most AOIs are not capable of solder inspection for these parts. So Bill is correct. He is also correct about referring to the IPC standard for QFN components. This is something your design Engineer should do when laying out the pcb. Refer to it for land patterns and dimensions.
(http://www.smtnet.com/Forums/Index.cfm?CFApp=1&Message_ID=66111)