I used 2048x1536@75Hz on mine, with a brightness and contrast settting of 45/100 respectively
The text and horizontal lines were a bit blurry at that setting, but it was a tradeoff for having the vibrance.
I had a few refurb ones before I got the brand new P275. The new one is MUCH higher quality than the refurbs.
The refurbs, had poor convergence, was much blurrier at high contrast settings, and the blurriness was inconsistent across the screen(one side would be blurry, and the otherside would be sharp)
I'm guessing you used 100Hz at 1600x1200. If you use 75Hz, it should be razor sharp at that resolution.
I personally don't see flicker above 75Hz, so it's acceptable for me.