Crossover is beat by the Qnix, better overclocking and generally just a better panel. Don't waste money on pixel perfect, all they do is refund you the difference if the one you get isn't 'pixel perfect', they can't open the monitor boxes to check.
Though Gsync is tempting, I personally think the ROG monitor is crappy value, especially given the fact that its a TN display.
The only problem with these IPS monitors that are OC'ed, is that their pixel response is so slow that it never gives you 120 crisp images. It all gets blurred. The problem with the ROG is that it is expensive, at least the predicted price is expensive, but we won't know for sure until it is sold.
G-sync may not end up selling a lot, as in a year or 2, there will be a non-proprietary version, but the tech will not die. It is just getting started. If you want variable refresh rates, the G-sync will work now, and will continue to do so for the life of the monitor. It isn't something dev's have to program, it just works, so you don't have to worry if another version takes over, yours will still work. The only downside is for G-sync, you'd have to stick with Nvidia, which may not really be an issue.
I personally would rather have the ROG monitor, but the predicted price is steep enough to make you 2nd guess buying it.