I got my NX last October just in time for the fall season. I must have lucked out and got a good one, since I've had no problems so far. The skimmer still does the bulk the work, as mentioned above. I run mine 5 hours a day, 10 to 3. But when the skimmer is off the NX is still our there picking up stuff well into the night using free energy. I also use my Polaris robot 2-3 times a week to get the bottom/sides. I think I'll appreciate it more during the swim season when the NX is getting those bugs, pollen, etc., instead of reaching for the small net to clean the surface. I'm more picky when we are actually sitting out there or swimming versus off-season when I'm just trying keep 99% of the stuff out of the pool. I've been thinking of taking a time lapse video, which would be interesting to quickly see how much it moves around.
Anyway, pricey, but no regrets here. Hopefully the battery replacement after a couple years of use won't be too painful.