I'm 5'10" and I'm fine back there. If the 2nd row is reclined, then yeah it is a little tight on the knees, but in my opinion it is just fine.
You have to consider how long someone might be back in the 3rd row. If you are going to be taking a lot of trips of over 4 hours, and you will need to carry 7-8 adults, then I would think an odyssey would be a better choice.
If you are normally hauling around a few adults and some kids around town to ball practice and the like, then it is fine.
Also, consider if the adults you will be transporting, if those people have to sit in the back, are they really tall? If so, not a good choice.
Basically 3rd row is cool for occasional adult use on short trips if they are not over 6 feet tall, and good for kid use all the time.
I sat in my friend's odyssey in the 3rd row just yesterday and I wasn't all that impressed with the space. The seat is right there in front of you - made me feel claustrophobic a little.
To me the pilot's 3rd row is very usable.