First is the pre-applied paste, just bin it and repaste. The pasted area is not big enough to fully cover the lid of a 3900x. Whilst troubleshooting some temp issues (more on that below), I ended up removing the cooler from the CPU only to find out that the paste didnt cover the entirety of the lid. Some might argue that it covers the chiplets but I prefer to see a full covering. Repasted with Noctua NT-H2 and reduced my load (AIDA64 Stress test) temps by 4-5 Degrees.
Secondly, if you're putting this on a Ryzen chip, setting fan curves based on CPU temp is a pain. Due to the spikeyness of "idle" temps on Ryzen and a lack of any kind of hysterisys control in the CAM software, at idle CAM reports temps jumping around from 36 to 51 degrees, compared to Ryzen master, CAM is often reporting anywhere between 10-15 degrees higher temps. The spikes in temps at idle is a known thing with Ryzen but I really feel like CAM needs to be more intelligent in monitoring AMD temps or to have some hysterisys control so a quick spike doesnt send your fans spinning up and down all the time. For now I have set fan speed based on liquid temps instead. Under load though the temp readings are fine and generally match Ryzen master.
My other niggle is with the CAM software, the display you have is fixed, so you can have CPU, GPU, Water temp or a CPU/GPU combined stats. What I'd really like it to be able to cycle through different stats screen on a timer. I'd also like to be able to pull data in from other sensors that my mainboard exposes... can't be that hard since I see them all in Corsair iQue.
Pump is a little buzzy at 95% and up but I suppose that's to be expected.
Other than those things, I really do quite like it... sure it's expensive but for a showpiece you can't beat it.
It would be unfair for me to rate the cooling efficiency since I ditched the provided fans for corsair LL140s and I dont think they are really capable of pushing as much air as the included NZXT fans. That said, running Cinebench R20 over 10 minutes, temps stabilised out at 75c and AIDA64 runs of 15 minutes saw peak temps of 84c, probably not too shabby for a 12 core processor doing double overtime :)
If like me you intend on fitting this in the top of a Corsair Crystal 680x case, don't bother with the premium EPS cables, there's just not enough room to fit, I ended up installing the cables that came with the PSU in order to get it to fit and even then it's tight.