Well I went to the dealer yesterday and drove a Quest LE. I originally went to take measurements to compare it with the 3rd and 4th gen Ody's and the 3rd gen Sienna, but I ran into the same salesman I met on one of my other visits and decided to try it out.
Special thanks to Cliff from Exton Nissan (Pennsylvania) for patiently and non-pressuringly putting up with my exhaustive study. I believe I mentioned my un-impressed impression of another Nissan salesman I met at another dealer in the second set of photos, earlier in this thread.
Now, as the first and only (unless I missed someone) member on Ody club to drive a Quest, I am going to try and give as much info as I can. I looked through both an SL and an LE. (equivalent to an Odyssey EXL and Touring or Sienna XLE and Limited) I have to say I learned a lot more than I had on my other visits with the Quest. I know this is a long review, but I figured there are pages upon pages worth of comparisons of the Ody and Sienna. I am going to try and fit it into 3 posts. The first with background info, the second with pictures & measurements, and the third with the test drive. I have been looking at both the Sienna Limited and the Quest LE as possible vehicles to retire (not replace) the 06 Ody in the next few months, but I'm not in too much of a hurry. Now I understand that many people don't exactly like the Quest’s styling, but if there's anything we all should have learned this year it is that styling is very, very subjective. Personally I don't mind the Quest's exterior all that much. I don't love it the way I love the looks of the 3rd gen Ody, but I also don't love the looks of the 2011 Sienna and I can't stand the lightning bolt beltline on the Ody, among other things. It has been a long time since I have had to really look into other manufacturers since I have spent over half of my life being a loyal fan of the Odyssey. (How many people here can say that? Hint: anyone over 32 is automatically out of the running

) But when the 2011 Ody concept was released last February, I realized I had to start looking.
I suppose I should explain my needs for a little background info before going further. I buy vans for comfortable traveling. I drive over 30k a year and 90% of the time I'm the only one in the car. I also want to be able to carry 3 passengers comfortably and have a realistic 3rd row when I need it.
I should also say that the Quest will not be for everyone. If you have kids, the LATCH set up is not going to be a selling point over the Ody. If you want to haul huge amounts of cargo with the seats folded/removed or carry 8 passengers, the Quest is also not going to be on the top of your list.
I don't have kids, so I could care less about the LATCH system or being able to fit 3 car seats in the second row, however, Honda deleting that inner armrest was pretty much a deal breaker for me since the center isle has been clear in my Ody since day 1.
When I started looking at other vans, I naturally looked into the Sienna, the same direction everyone seems to be moving. It’s a nice van, but I had the same common issues many people have already noted. Things like the driver's seat comfort, off-centered steering wheel, and cheap looking dash are among the biggest complaints. I also didn't like the extremely low ceiling in the 3rd row, especially with the rear sunroof that comes standard on the Limited. I will say that technology and luxury features wise, the Sienna is hard to beat with the Laser Cruise Control, power folding mirrors, rain sensing wipers, auto high-beam, etc. From what I have observed however, as nice as some of those features seem, it’s hard to get passed the cheaper interior. Also, when I say cheaper, I mean more than the dash materials. From all of the Sienna's I have seen, things just didn't seem as solid. There were buttons that were loose and you could "wiggle" without pressing them. The side map lights had just a solid white plastic cover, rather than a textured clear cover. I know a lot of this is personal preference, but the more I saw of it, the more it felt like a kids car. I know, I know, it is a kids car, but it seems more like a kids car than the 3rd gen Ody did/does, which is a shame because I really wanted to like the Sienna enough to get it. It’s still not entirely ruled out, but it would have been a solid sale if it weren't for these issues. One major problem I found in all of the Sienna's is the HUGE blind spot when changing lanes and looking out the passenger’s side toward the rear seat. Depending on the way the backseat is positioned, it could be 2 or 3 feet of the vehicle's length you cannot see......YIKES...... I then thought the blind spot monitoring system would compensate for that, then I realized the Sienna doesn't have it. It offers laser cruise control but not blindspot detection.....but that’s another story.