220 cd/m2 is bright enough to hurt your eyes if viewing for extended periods of time. Regardless of maximum brightness, professional use needs 100 to no more than 140 cd/m2 as a white point depending on the nature of its use. At 550:1 that means you get a black of .4 cd/m2 which isn't bad but if it's to simulated printed work, .25 cd/m2 would be the gold standard. At the time the 21UX debuted 1600x1200 panels were still extremely expensive. Now that they've come down, that could use a shifted price rather than cheaper models used to reduce the point of entry.