Flicker. Anything less than 120Hz can give severe eye strain and headaches over long (30-60 min) work sessions.
As to the LCD replacements, the anti-aliasing is just not as smooth (yes, I'm being subjective) as on the CRTs. Perhaps, a "retina" level resolution display with 100+Hz refresh-rate will be a real solution. But those are probably still at the R&D stage and will be ridiculously expensive at launch! And the graphics cards to drive them as well!