I have that Tektro. I've found that mounting the stop higher (even on the steer tube) with the extra cross levers makes for bad cable routing. The stop mounted on the fork on my older bike works great. I can't imagine a headset mounted stop would work well at all, sadly enough. Just too tight of a curve for the cable.

As to why don't I run a disc brake? I have cantis. They work. If I need to change 'em I will, but so far I don't have a problem with them.