I have to say that i also agree it depends on the kid and trip... and the school. While we try to plan family vacations during non-school times, we've been fortunate enough to be able to piggy-back on my husband's work trips a couple of years running and, since those dates are set, we have to live with the fact that we are pulling the boys out of school.
Granted, it's only 1st and pre-school now (was K and daycare last time, so the latter didn't so much matter), and it may be harder as they get older, but for 10 days out of school - the opportunity to see a foreign culture, landmarks and experience different worlds - i see that as a no contest decision. The school has been very supportive and the teachers have been very willing to send homework for work that will be missed(usually gets done on the plane out!) and to request a "presentation" of the trip upon return. that seems like an absolute fair trade, and he (1st grader, which is really the most applicable) usually catches up so quickly when we return anyway, it's definitely worth it.
FWIW.