"In deciding when to publish, you will have to balance several considerations, but try to resist the temptation to rush into print, if you have a choice. Remember, the quality of your publications is what matters most in the long run. A paper that is incomplete or carelessly put together is less likely to be accepted for publication and will be an inefficient use of your time. Even worse, incorrect results will damage your reputation."
"Writing up an incomplete or flawed story is not time-effective, since writing a good or bad paper generally takes the same amount of time."
—Tom Misteli, National Cancer Institute
Quoted from: Making the Right Moves: A Practical Guide to Scientific Management for Postdocs and New Faculty
Of course, waiting until you have the "perfect" paper in hand before submitting is a luxury most of us can't afford, especially grad students in the twilight of that PhD. We need the recognition a paper offers to get funded, finish our degrees and move on to the next career stage. More established scientists, like Nobel winners, NationalHeroes and tenured profs can afford to be as patient as they want. But even for us lowly and desperate students, it's valuable to realize that to "publish or perish" is not always the best path to pursue. Getting a paper to your name is nice, but it comes at a steep cost. You'll only have so many papers in you, so use them wisely!