I have a Honda Odyssey, I bought it used a couple of years ago, and LOVE it. I doubt I'll drive anything else until my kids grow up, because it's just so convenient! I have also never understood the aversion to minivans. When I was in high school and college, my parents loaned me a car for my use, and it was a minivan. Even then, I didn't associate it with stigma. I could fit all my friends in there! Sure, I would have preferred a sports car, but... ^_^
Anyway, I test-drove the Toyota Sienna as well, and really liked it. In the end, though, I just prefer the way the Honda handles. The two brands drive very differently, but have equal safety ratings and equivalent features, so make sure you drive one of each and that will really make the decision for you.
Things I love about the minivan - well, more than I have time to mention. The auto-sliding doors, the ease of fitting car-seats in there (you could easily fit four, and since I have two and am thinking about another, that was important), the huge trunk space even when the third row is in use, etc. We have pets, so when we go on a road trip, we need that trunk for luggage and the animals can sit in the third row. Sooooo easy. I have plenty of storage, and I love that there is an 8th seat that can fold down when not in use!
I get somewhere between 17-25 MPG, depending on the driving.
Just to let you know, ReverendRuby is incorrect. The windows open in the front and middle rows, all the way, just like in a car, and this is the case for basically any Honda or Toyota minivan you buy these days, even used (I don't know about other brands). It is only the rear windows that don't open.