It was difficult deciding among Toyota, Honda and Kia. All have their good points and drive well. I bought the Toyota four weeks ago, and I am happy with the decision, though I'd probably be just as happy with the Honda and Kia. I have the blind-spot monitor option ($500) and like it a lot. On the Sienna it is on both side-view mirrors; on the Odyssey, it is only on the passenger side. The long-slide 2nd row seats allow for almost 19" of leg room in the 2nd row, though that would leave almost no leg room for the 3rd row. Both 2nd and 3rd rows have shades. Entune and navigation system are great. Lots of cargo space behind 3rd row. 3rd row seats store easily, but not as easily as Honda's.
I've had this car for 2.5 years now, and I am highly satisfied with it.
TWO YEAR UPDATE:
We initially leased our Sienna because it was our first minivan and we were unsure if we'd like. After two years, we loved it so much we bought out the lease. While at the dealership, they offered us $4,000 more than the buyout because the fair market value of the vehicle was so high. We decline their offer and kept our Sienna.
After two years, we had zero problems with the van. The kids like that they can easily get in and out of the van by themselves, and close the doors. We've driven it cross-country and it excels in that role. There's plenty of space for luggage, tons of cupholders, good highway fuel economy (26 mpg), and a comfortable ride. My biggest complaint is the small screen for the backup camera. That's not really the van's fault, as a larger screen was available when new and I declined that option.
My wife's favorite feature is the storage spot for her purse. It rides comfortably below the center stack. The front or rear seat passengers don't have to hold it and it's out of the way but easily within reach.
Our Sienna is the vehicle we should have gotten years ago instead of an SUV. It is incredibly practical despite its geeky image.
The interior is often a sore spot in Sienna reviews, but many confuse a minivan with a Lexus sedan. The hard plastics in the Sienna are designed for contact with snot-nosed kids with their greasy popcorn hands. The interior of the Sienna is much easier to clean and will hold up better to hard use compared to something with soft-touch plastics.
The Sienna does not have the reliability problems that the Odyssey has. Honda V6 powertrains have a history of eating transmissions and, lately, engines. Too bad, because the rest of the Odyssey is very nice.
I purposely looked for a "base" XLE without Navigation/Entune or rear entertainment (DVD) to get the more comfortable leather seats (front only, rear softex) and minimize options which would be expensive to repair after warranty. This is my second Sienna, with a 2011 Odyssey purchased in between. I've read comments about the Odyssey being a better van, BUT my 2011 Touring ended up having transmission and engine issues, and it was an expensive vehicle. The Sienna has a great engine/trans combo, and the interior is very comfortable and spacious.
I am pleased with this car, 15k miles in except for the run flat tires and lack of a spare. the AWD versions of these vans have this serious design flaw, and the run flat tires are twice the price of standard tires, and wear twice as fast. So the buyer can figure on a factor of Four times the expense for keeping rubber on this car. As a lessor, I am disappointed that I will have to buy tires at least once for this car, and the run flats are absolutely awful for AWD traction and performance once they get to 4/32.
Decent minivan. After owning a Honda this was our first Toyota minvan. Most of the features we have been happy with. The BIG disappointment is the run-flat tires. I'm not sure why Toyota has stuck with them so long. The cost 2.5X times normal tires and wear out in 25K miles! This is a huge maintenance cost and bring the total value of the car way down. I'll never buy another car with run-flat tires.