For the tall rider, it makes all the difference. ALL the difference.
The 2007 650 I bought, had a Utopia backrest that seemed comfortable enough. Even though my knees were being driven into the glovebox door. It had the right posture for me; but my knees were smashing the plastic; and that's just as well because I felt forward enough that I thought, in winds, I was sliding off the seat.
It seemed tolerable in a 30-minute test ride. After a couple hours on the road...I was really, really starting to think I made a mistake.
But the Isuzu headrest/backrest does the trick. Removing the butt-stop gives me exactly the legroom I need...PERFECTO! And the backrest goes right into the hollow of my back - right where I want it. It braces; supports; has a little give, which is good.
Now...it's not perfect. You feel some lumpiness in there; it's not a pillow or a Corbin seat. But with a riding jacket...it's not an unpleasant feeling. Actually comforting...firm support; lets you know it's keeping you in place.
Totally worth the $65 in terms of comfort. How it holds up, with the modified rods to slide into...that remains to be seen; but even if the PVC pipe-sliders wear out or crack, replacing them should be no problem. The actual headrest/backrest should hold up for years.