Here's a good column about the negative impact of too much homework on young students, which prevents them from excercising -- either their bodies or their imaginations -- and negatively impacts family life.
When my children were in public elementary school I found that their homework was usually either pointless busywork or something that the teachers wanted the parents to teach; that was one of the things that gave me the idea to homeschool. If the teachers wanted me to do the teaching anyway, why not just do it during the day and not go through the agony each night?
One of the things I love about homeschooling is that, with one-on-one interaction between parent and child, it's possible to study a subject intensively in a relatively small amount of time, with plenty of free time left for enrichment, leisure time, and family life. (My youngest son has been learning woodworking in the shop with his dad of late and jokes that he's "taking an elective.") And no more homework ruining Christmas vacation!