We have a Toyota Siena 2006 LE. LOVE IT! Bought just a few months before #2 was born when hubby's car died. Planned to buy it in April, but bought it in Jan a few months early. We did all the research and it came down to the Honda Odyssey and the Siena. In the end we picked the Siena because it had a longer safety track record for the braking system. Honda had some issues with their braking system a few years back. Plus all of our other cars are Toyotas, so I guess we are kind of biased.
I use the Siena as my everyday car to tote the kids around. We have a 4.5 yo son and a 2.5 yo daughter. This past May we took our first major road trip from San Diego to S. Dakota. 3 days of driving each way. The kids LOVED IT! We fit everything into the rear of the van with no problems. Didn't even have to put anything up top on the luggage rack. We just folded down half of the rear seat. We had 2 weeks of Winter clothes, 2 weeks of food (we have food allergies), toys for the kids, our Bob stroller, etc. This year we plan to make the same trip again and will bring the kids bikes and scooters. We were all comfortable in the van during the 8 to 10 hrs of driving each day.
My parents have a Highlander. It's a great car for them. And my kids car seats fit nicely into the rear seat when we are visiting. But it can only fit 2 car seats and the 2 front seats. So only 4 people can ride in it. With the Siena we can safely fit 2 car seats, and 5 adults. The Sequoia just felt too big and bulky for us. The Siena fits us just perfect. We can take the long road trips, can drive the grandparents around, can haul furniture, and still be safe and comfortable.
My hubby gets carsick whenever he sits in the back seat of cars. Although he rarely sits back there in our van since he is usually driving or sitting in the front passenger seat, when he has had to sit back there he hasn't gotten sick. My Dad sits back there the most and he also gets carsick a lot and has not gotten sick back there. So I'd say the Siena has a pretty smooth ride.
If you buy in Jan like we did, you can get last years model at close out prices. We got an awesome deal on our 2006 model in Jan of 2007.