I think anyone building a high end Rig should consider sealed water cooling.
The first is obvious; leaks. Even with so called "sealed" systems, leaks can occur. Hoses can crack or get cut, fittings can come loose, or there can even be a manufacturing defect. The problem is, and I've seen it too many times, users are very conscientious in the beginning. And for the first year or two, they regularly check for leaks and coolant levels (for non-sealed systems). But being new, there rarely is a problem so instead of checking regularly, they slack off. That's were the trouble begins because flexible tubing hardens with age, becomes less flexible and can become brittle. Fittings can work loose and spring a leak. As the equipment ages, regular inspections should increase, not decrease.
The second reason is much less obvious. Motherboard designers and engineers intentionally cluster other heat sensitive/heat generating devices around the CPU socket so they too can take advantage of the "expected" downward firing OEM cooler. These devices include the regulator and voltage divider components and even the chipset (as many don't have their own HSF assembly). This is why I don't really like side firing 3rd party coolers either - they only blow in one sideways direction, and not down and about.
So what happens is these users implement alternative cooling solutions for their CPUs but totally neglect "case cooling" and the cooling requirements of their "system" components. All they really achieve is bragging rights for their CPU temps. In the meantime, their motherboard components are being abused by running at least very warm (if not hot) most of the time. Which, if nothing else, increases aging of those devices.
I am actually a fan (no pun intended) of today's OEM coolers. They are not the same as OEM coolers from years back. As I noted above with TIM, neither AMD or Intel (or NVIDIA) want their processors to overheat, become unstable, or worse, be damaged. So contrary to what many still believe or have been told, the OEM coolers are more than capable of providing adequate (and pretty quiet) cooling for their processors, even with mild to moderate overclocking. And again, I stress it is the case's responsibility to provide an adequate supply of cool air flowing through the case. The processor cooler need only toss that heat into the air flow. And a good case will suppress fan noise too! (Love my Fractal Design R4 )
So I say, unless doing extreme overclocking (or your CPU does not come with a cooler) try the OEM cooler first. You may be surprised that it does the job quite well.
The popular CM Hyper 212 is only warrantied for 1 year! OEM coolers are warrantied for 3 full years - not just in case they fail, but to protect the processor they come with too. In the rare event a failed OEM cooler causes CPU damage, ONLY the OEM makers cover replacement of the CPU too. No aftermarket cooler warranty covers damage to or replacement of the processor!
And to that, it is also important to note that cooler temperatures does NOT automatically mean better! You can tell by the last line in my sig that I take heat very seriously! It is, no doubt, paramount that CPU temps remain comfortably within the "normal" operating range. But there is absolutely NO EVIDENCE or scientific reasoning to suggest that a CPU running at 30°C performs better, is more stable, or will have a longer lifespan than it would if running at 55°C. All that extra 25° really gets you is bragging rights. Nothing wrong with bragging rights - as long as the one bragging really understands what it is they are bragging about - and cooling of other components is not neglected.
So unless my client insists on alternative cooling (or selects a CPU that does not come with OEM cooling) I always stress to use the OEM cooler first. Get a good case and ensure it is equipped with quality (and quiet) fans. Then keep an eye on the temps. An aftermarket cooler can always be added later.
The other exception is with our "silent running" HTPC builds for PCs going into home theater setups. I almost always just go for some form of "passive" (no fan) cooling then.
As far as shipping computers with CPU coolers attached, I just don't do it any more. In fact, I don't ship anymore at all. Like William, we are local only now and either I take it to the client myself and set it up there, or I instruct and caution them how to lay the computer on its side so the HSF is sitting on the board, not hanging off it.