I have been using the nano coated one since June. I am noticing no difference in the cup taste. It does make a cooler looking raindrop pattern when you run water through it without a portafilter. Plus, since it's "precision", it gives you a feeling of satisfaction that you have something precise.
As to mods to the machine. It's already supremely capable as is, right up to the point of being almost but not quite a Slayer-type flow profiler if you want to use it that way. If that's not enough, a very simple and reversible modification can turn it into a full blown, Bianca-like flow profiler, where the whole shot runs through the factory needle valve. And if for some reason even that is not enough, you can experiment with different needle valves. Read this thread:Breville Dual Boiler "Slayer shots"?
Discussion of the actual mod begins on post #161