Just a heads up:
This one probably won't affect most people, but it means that I can't load N3 projects in N4.
I have 3 slave machines, each with Vienna Instruments on them. Therefore the .dll are named ViennaInstrumentsA ViennaInstrumentsB and ViennaInstrumentsC respectively. When I load a VSTi I therefore know what machine I am loading on.
In N4 I can only "see" one ViennaInstruments at a time. So even though all three are in the appropriate VST folder, only one appears in the VSTi list. As soon as I delete that one from the folder then another one appears.
I have had to go back to the original .dll, all called ViennaInstruments, and search the network for the appropriate machine.
I'm going to set up a load of MIDI track presets, but inevitably there will be times when I need to load a new instrument for which I don't have a preset. So the new system will slow me down.
I'm going to do a bit of a hack so that I can still load N3 projects in N3 and maybe save some presets to load in N4, but this really shouldn't be necessary.
So my warning is, even after you've pointed N4 at your vst folders, don't expect projects to load if you've done any renaming of .dll files. Strangely enough this problem doesn't occur with Chainer. Maybe it is not a problem with effects, only with instruments.