[dugmartin]

How about giving your new hires a few mostly blank pages with a letterhead of "My first two weeks WTF moments...". On day one give it to them and let them know you will take them out to dinner in two weeks to talk about what they write down. Let them know it is really valuable to you to have fresh sets of eyes on company processes and that there will be no negative repercussions. I'd then give them a few examples of what you would like to know.

Given all that I still think you won't get much feedback until you've done this a while and the current employees let the new hires know that there are no issues with them telling you that things are wrong.