I had a good time when I was young and my memory's not what it used to be, but I believe the KLR is the first DS bike I've had that even had a tachometer. Thus, the only time I ever paid any attention to it was during the break-in period.
I did watch it today and I generally tend to shift between 5000 and 5500 and at 75 indicated I'm running around 5100-5200. When not on the Interstate, I seem to usually be in the 4K range at around 60 or so.
Simply based on sound, feel, pull, etc. mine seems to be "perfect" around 3500 to 4000 rpms. I don't intentionally look at the tach to keep it there, but when it feels good and I look down, that's generally where it is. More or less.