It definitely depends on many different variables.
For us (Canadian)...
Our schools were very free and easy, no truancy officers or courts. Parents have almost complete authority over their children's attendance - a lawyer friend of mine said the only time she sees the truancy laws applied is when there are other issues bringing the family into court (abuse, neglect, etc).
One of our children was an excellent student. The other was dyslexic, and struggled in school. Both were in the district's congregated gifted program.
We always asked our children whether they wanted to take time off school for a family vacation, and let them decide. We trusted them to know best whether or not they could manage it. But, a large part of that has to do with the fact that our children were voluntarily choosing to attend public school, after having homeschooled for several years in elementary. They took their schooling very seriously.
Teachers were always supportive, even encouraging. In grade nine, my son's Special Education Resource teacher tracked me down to ask when he'd be taking some time off. The teacher said he'd noticed my son was under a lot of stress and felt he would benefit from a vacation. That same year, in grade 10, my daughter was waffling over whether or not to visit Disney World with us. She discussed it with her Chemistry teacher, whose response was, "Are you crazy? You'll be way too busy to go next year, so you should grab the chance and go now. Go! Go!!"
As it happened, that year was the last year we pulled the kids out of school to visit Disney World. The next year (when they were in 10 and 11), they both decided they were too busy to take any more time off.
Finally, I don't happen to feel that attendance is in any way a moral or character-building issue. Learning happens everywhere, not just in school.
Personally, if the school and/or legal system allows it, I think most kids can benefit from family vacations during the school year. Your kid doesn't have to be a straight A student. In some ways, I always felt as if my son, having to work twice as hard as anyone else just to keep up, deserved a break more than anyone.