Thanks for your posts, everybody. Yes, it would be rational to wait until you hear from the first choice school. But here is a more difficult dilemma. Suppose you are on the waitlist of your top choice school, and you have received an offer from a less favorite school. You want to wait until the deadline, April 15. But a guy who has received an offer from your topic choice school rejects it on April 15, and now you will get an offer from it on, say, April 17. But you cannot wait until April 17, because you have to accept the offer from the less favorite school on April 15 to be safe. So you will never get into your most favorite school that keeps you on the waitlist until after April 15. That is a real painful situation. What do you think?