I have a 2004 8 pass sienna and I love it! We've had it almost a year. Every time we take a trip longer than 10 miles or have to load anything, I mention how much I like it. For us, the 3 across the second row is so nice! We only have two kids, but they can sit side by side and their is plenty of comfortable space for a parent. That is so valuable on road trips! Plus, if we have a 3rd at some point, we have the option of keeping all of them close by.
It has a ton of cargo room also. We just took a 5 day trip and all our luggage, including a stroller and a mealtime booster, didn't even come close to reaching the top of the back seat. We've actually even folded the 3rd row flat, removed the second row seats, and all slept in it. We fit a giant rolling toolbox even with the second row in use, and we've also had a ladder in there. My husband has loaded a mattress and box spring in it.
The only thing I don't like is the downgrade in mpg. I used to drive a little car. I get about 18 in town (big city, kajillion traffic lights) and 24-25 on the highway.