At the Mysterious Matters blog , a mystery editor shed light on common reasons for manuscript rejection. Apparently at their office, they keep a database of all the works they turn down. On reviewing this database, this editor realized that there were certain words used over and over again in their in-house comments on these rejected manuscripts. Be sure to read the article, which explores each word in depth, but here is an overview: Pretentious, derivative, self-indulgent, slow, forced, ho-hum, inane, depressing, amoral, dull.
The ho-hum was a little disturbing to me. The editor commented: 6. HO-HUM. A ho-hum manuscript might actually be a good book if you were stranded on a deserted island with nothing to read but pulp fiction. It has all the right elements but doesn't manage to rise above the everyday formula. Sadly, a competent, ho-hum manuscript won't make it in this cutthroat era. If we can't get excited about it, we're not going to be able to get readers excited about it, either.
It just goes to show you really do have to go the extra mile with your manuscript. Even if it's good, it has to be great to pass an editor's requirements these days.