My sample of the 10mm f/2.8 is much better than what Richard and Øivind describe. True, corner performance is lower than the on-axis result, and this becomes more visible for distant focus settings. However used at middle-near range, even corners aren't that bad.
Like Øivind, I'm using the 10mm f/2.8 AW1 mainly combined with the Olympus fisheye converter (he gave me the tip ...) and this lens is also quite good, albeit corners are somewhat weaker. Corner performance again is better at near range and that suits underwater shooting well

I wonder about the quality control, or lack thereof, of the cheap CX Nikkors, in particular the zoom models. The 10-30 kit lens as an eample: a decent performer if you are lucky, otherwise very mediocre. Both situations can deteriorate over time since the lenses are highly susceptible to wear. The 10mm versions stand out being much better in this respect, and the 11-27.5mm AW1 also appears to belong in this category as do the 18.5mm f/2.8 and the 32mm f/1.2.