Definetly a great family movie my kids thought it was great.

I saw it this weekend with my family (2 boys ages 5 & 7) and we all LOVED the movie!  The messages are great (for example, the main characher is a sensitive & unpopular kid who uses the special gifts that made him an outsider to save the day.  Also teaches that everything we KNOW to be true can, and sometimes should, be questioned.  We also learn that just because something looks evil (the dragons) doesn't mean it is evil).  

The visuals are spectacular (I highly recommend seeing it in 3D if you can - it's gorgeous!)

There are some kind of intense scenes with the dragons (some where they're attacking the humans and some where the smaller dragons are battling a huge dragon).  We went with another family and their 4 year old girl asked to leave about 3/4 of the way through because she was scared.  My 5 year old said afteward "I was a little scared of the big dragon but I just told myself 'it's not real' and then I wasn't scared".  You hear about how dragons have "killed hundreds" of vikings but you never see anyone die.  Several characters have prosthetic limbs but you don't hear much about how they lost their arms/legs.

If your kids are ok with StarWars and other movies like that (non-human creatures battling with loud noises) they'll be fine and will probably love it.  

Oh (SPOILER ALERT!) the girl kisses the boy a couple of times during the movie.

Hope this helps!

You didn't see the review I posted on PluggedInParents.com? :) Hands down, it's one of the best family films of the year, enjoyable by both kids and adults. I recommend elementary school age and above, but I feel even a few younger kids would have no problem. I explain why in my review:

Our Review! http://readingteen.blogspot.com/2010/03/how-to-train-your-dragon-movie-review.html

this is good movie for family