I'd love to try this lens but my remote location precludes testing or renting. MF and aperture don't scare me. Are you aware of any reliable tests on this lens?
DXO give it a stellar rating (for the Canon mount version at least).
There are plenty of other tests of the Canon mount version I can add, but haven't looked for any Nikon reviews myself.
I just got it in a Canon mount yesterday. Whilst I haven't had time to give it a really serious test, the initial shots I've taken and looked at suggest everything written about it is correct. The possible exception is quality control, as mine appears to have a correct focussing scale, so it might be even better than some early reports suggest.
Using a correction profile in Lightroom deals with all the curious distortions.