Writer's Fallout Shelter

Liam started this thread over a year and a half ago, but I have found myself in a position recently where I am the one writing and sending out the rejection letters. At least 90%, probably more, of the rejection letters I send out are form and the form letter I use basically says, "Don't assume it's you; it's probably us." It's funny and light-hearted. However, sometimes I feel compelled to send out a personalized rejection. In those cases, I find myself in a dual-frame of mind.

One one hand, as the individual doing the rejection, I feel the need to be honest. Obviously, there's something that didn't work about the submission, or else we probably would have accepted it, and it seems that telling the writer what it is can only help them improve and better target our publication, but sometimes, when I'm typing out the reason, my writer-brain kicks in and I think, "Gah! I hope they don't find that too harsh, too honest, too truthful. I hope it doesn't send them scrambling for the B&J and Makers."

So you tell me, if you're to receive a personal rejection, rather than a form rejection, how would you want to receive the news?