Got my '06 last Sept and it came with a Corbin on the front seat. I've been riding it with the Corbin almost daily. I've had a Corbin gunfighter on my FJ for a number of years and a lot of miles. Its the flat, smooth gunfighter. I've seen a number of different styles of Corbin for the FJ, and I'm assuming you can get almost anything for the FJR, as well. Not sure what Corbin came on mine, but the PO did say he mod'd it a bit to lower the height. He and I are both vertically challenged at around 5'7".
Well, I decided for grins to put the stock seat on for today's commute. What an all-around POS! I felt like I was riding in an early sixties pickup truck. Bouncin' all around, up a lot higher, and feeling like the seat wants to wedge itself up my ass.
Now the Corbin I have isn't perfect, it tends to slide me into the tank, squishin' the vitals, and there's a little more weight on my arms. But its flatter and I can move around on it and its definitely is a lot lower. Good for getting my feet down and also good for being able to hunker down behind the windscreen with it fully up on 18 deg mornings like today.
I can't imagine keeping the stock seat on for any reason. I've never tried the Russell or any other seat, but they may be worth looking into.