I've never had a 15Khz monitor as I wanted to use interlaced modes without flicker.
I currently use a 15" NEC Multisync 3V (30Khz) and 21" NEC Multisync XE²¹ (30Khz). Both are very good, image quality is let down slightly by the external scandoubler going from RGB to composite and back to flicker-fix the image.
Next monitor for me will be a large LCD panel - flat screen (less reflections), continuous refresh rate (for zero flicker), high contrast (no need for a screen filter), low energy (saves bills), low heat (good if you want to control room temp.) and space saving. Oh, and they don't create a large magnetic field or deflect static-charged particles at your face.
:-D