The rear-dvd was actually the only option that I didn't require when I was looking for my YD. Esp since I'm single and don't have any kids. The YD I really wanted just happened to have it though. Even the sales person was like, "oh hey, do you have kids?!" After I responded, "No," she was like... "oh... well... it has a rear DVD player!"

But trust me... kids aren't the only ones to like to watch movies on a trips!
My friends/family love it when we go on any type of trip where we'll be in the truck for awhile. If I have the 3rd row in, they can see the screen just fine - even though a 7" LCD does seem a bit small. Also, the extra features that come with being integrated it nice; since it allows folks in the back to listen to it via the IR headphones, while the driver/passenger in the front can listen to something else - CD, FM, XM, etc. And you can add more IR headphones (it comes with 2).
It does pretty much block the entire rear-view mirror, so I only have them flip it down when we've gotten onto the highway and it won't be as important.
But now... for some reason, I just seem to get volunteered to drive anytime we go on long trips... interesting...