I've pretty much have had mostly good luck with pre-orders. My LHS has never got it wrong except once when I gave up asking when my engine was in. Another year went by and it had been in his case and was being demoed to other customers. When I finally asked again and he pulled it out of his demo case, I did not accept it as a new pre-order and did not buy it because it wasn't brand new any more and I was kind of mad about it. His mistake was he never called me to tell me it was in. He did, however, order a different engine that was in stock at MTH and gave me the pre-order price -- so the love was still there and I continue to buy from him because they're a great shop.
I do like pre-ordering with the the online sellers like Mr. Muffins or Trainworld because they will exchange emails to confirm or actually have a check out receipt for pre-orders. This eliminates that question, "Did he or didn't he remember to write that down", and it also confirms the pre-order price in writing.
