Pros: Replacement Kraken x40 still working as of this date, 5 years later almost! I am extremely cheap and rarely upgrade parts but after the initial shock of my motherboard being fried and asus sending me a replacement I am still using this cooler. It has been on 8 hours a day almost 7 days a week since 2013. I know its too late to make a difference as this product is no longer manufactured But I can say the reliability of this unit has been phenomenal, not a single leak. My next cooler will be a NZXT ring.

Cons: cam software not the best. Speed control for fans doesn't seem to work so I just plugged them into my case's fan controller.

Pros: Quiet.

Cons: I have joined Newegg to warn other customers about NZXT products. Not something I normally do.

The company lie about case compatibility. Their head of Tech Support (Eric Henry) has stated in an email to me they do not test these on any cases but their own. This makes their compatibility list totally false as I found out a few weeks back.

I have a Corsair Carbide 500R and their compat guide states rear placement. Their head of tech stated in an email to me he had the case in front of him, and it fits fine. It took me sending him a video and photos to admit he had 'got it wrong' and that it doesnt fit. They have offered no compensation, and advised me to chop my case up to make it fit.

Disgusting customer service, and would most definitely never buy NZXT products again.

Other Thoughts: Customer service from NZXT is completely abismall. I would not recommend any of their products based on this experience. Being told to cut up a case that is worth more than the cooler itself is an outrageous statement to make, especially from the head of tech support for the company.

Pros: CPU:
Kept my i5-2500K OC'd to 5GHz under 70°C during stress testing.

GPU:
With the NZXT Kraken G10 bracket it keeps my MSI GTX 780 Gaming OC under 50°C at full load even when overclocking. Control panel is very simple, yet provides full control of the cooler.

Cons: Fan has a very annoying motor whine above 30% fan speed. Not high pitched but very annoying none the less. USB connection caused BSODs after 8 months of use.

Other Thoughts: After about 8 months I started getting BSODs. I changed boards, memory, graphics cards, SSDs and HDDs. I even reinstalled Windows 3 times and the BSODs continued. I finally unplugged the Kraken X40 USB cable and the BSODs stopped. I plugged it back in and the BSODs returned. It's unfortunate because this cooler does an amazing job, but the problems it caused are unacceptable.

Pros: Does what it is made to do.

Cons: None. although when I bought it NZXT announced that it was releasing the Kraken X41 the following day! I would have bought that had I just waited 1 more day.

Pros: I recently built a new system and my i7-4770k was idling at 140 F! After reading over my available options I went with this cooler because NZXT makes my case and I have been happy with it.

My machine was already built, so installation was as simple as removing my current heatsink and installing this one.

After installation my machine idles at 90 F and I couldn't be happier.

Cons: Like others have mentioned the fan can be loud when it runs at max. However, my system has yet to push the fan to max, even when I play FFXIV on on maximum settings.

Other Thoughts: My Asus Maximus VII required some BIOS modification before the system would boot without a "CPU Fan Error." I had to tell board to ignore cpu fan speed.

Pros: Amazing cooler. Replaced my 3 year old Antec Kuhler 920 and its even better then my old one.
Got another fan exactly the same for push pull, playing games like WoW and its sits at 29c very nice improvement from a 120mm.

Cons: Make sure you have enough clearance, i had to loosen the screws and push it toward motherboard and tighten them so the side panel would close correctly.

Removed thermal paste and use my IC Diamond.

Other Thoughts: Computex 2014 just announced new X41 and X61. Thicker rad, pump, etc everything brand new and upgraded, except the tubes, but it will be a big difference.

Only regret is getting this before knowing a new version is coming soon.

Pros: Pretty much fell in love with this thing when I first saw it. The NZXT logo LED is way better looking than the Corsair one, in my opinion. Official reviews showed that this cooler outperforms most of the Corsair ones as well.

With the stock fan installed and with the Extreme profile selected in the software, this thing is a seriously good cooler. I put it in a Node 304 and it kept my 4.1 GHz 3570K at around 35-40 idle, and never above 65 at full load.

The tubes are pretty long. I love the idea of putting this radiator at the intake side so you guarantee it is getting cold air. The tubes are long enough to do so in a larger case. See cons also tube cons also.

Cons: I originally bought two Phanteks fans for push/pull with this. I eventually tried the stock fan in pull config. This fan is definitely too loud. Even at the "silent" setting there is a somewhat annoying whir. At extreme it is like what the other guy says, a jet engine starting up.

I would definitely recommend getting a different high rpm/quieter fan, it will still perform well. Pull config will suffice.

Another thing that was a con for me, but not worth taking another egg off, was that the tubes were too long. I had to pretty much squish them into my case.

Other Thoughts: This was my first Newegg review and first AIO cooler. I would have given this 3 stars due to the noise, but I just liked the looks of this thing too much. Ended up deciding I didn't like water cooling so I replaced this with an air cooler which is turning out awesome.

Pros: Keeps a big i-4820k cool. Really cool actually- house ambient temp 68F, idling CPU temp only 75F; or 28.5 C. Under max load does not hit 50 C.
nice sleeving on all connectors including the PWM fan.

Cons: The PWM fan that comes with this cooler can get pretty loud. A little tweaking brings it down to a dull roar. Not much of a con, really, as nearly all of the AIO water cooling units I've tested come with a mediocre fan.