I'm not, thank God, on the submission round (yet) but I do believe I'm still reeling from the first one. To receive a form-rejection letter is soul-destroying. Agents who never reply is heart-breaking and agents who ask for the whole manuscript and then keep you waiting months and months without a word is enough to make the most stoic fall apart.
That is why a writing friend is posting "rejection misery" on her blog: http://www.marileebrothers.com/index.html Some of the examples (except mine which is made-up) are unbelievably rude and uncaring.
Some years ago (here we go into the good-old past when we only had telex) I worked in the recruitment department of a huge multi-national which received hundreds of letters soliciting jobs that weren't advertised (a slush-pile if you like). Every letter was answered within a week - there weren't form letters, every one was typed and sent by post (OK, they may have all said the same thing, but at least they were short and sweet). If a person was interviewed then every three weeks he was sent a follow-up. Even the guy who replied with, "If you haven't got a job for me, then CREATE one" received a polite response.