I just used my third row for the first time, thought I'd report. I fit 4 adults and two kids in car seats into the truck. That, by itself, is pretty amazing. We were able to avoid having to take the car seat in and out to access the third row by climbing in through the back. It took a little gymnastics, but better than moving the car seats. Obviously not ideal for an everyday 6 person vehicle, but for the odd times when you have family visiting, it is worth it. We saved $300 on a rental car. If I do that 3 times it pays for itself.
And one point, the "downside" of not having any cargo space in the back when you raise the third row is not actually a downside. Obviously, if you want the cargo space, don't put the third row up. The third row is simply an option that you can put up or down as and when you decide. If you have 6 passengers and little or no cargo, you'll be glad you have the third row. If you have 4 passengers and some cargo, you can put the third row down and be fine (just like a 4R without the third row option). If you have 6 passengers and a lot of cargo, the 4runner just isn't the right vehicle and you can't blame that on the third row option.