Comments from someone who has mostly air cooled but has recently moved to water cooling:
"Watercooling is hassle" - that depends on perspective, and what you want from your computer. It's definitely more hassle than air cooling, but so is building your own PC instead of buying from Dell. If you are looking for bang for buck, then I would agree initially air cooling is a better option. However, If you keep your rad, pump and reservoir for a few upgrades, and overclock your system to lengthen the effective life of your CPU (upgrade 6-12 months later than you would have previously due having obtained a higher overclock) then water cooling can start to seem more financially viable. Well, that's the theory anyway. To be honest, you could spend more on quality fans for your radiator and fancy case lighting than you would a decent CPU heatsink and fan. I won't even talk about the investment of time.
"kits perform well and are much more convenient" - I myself went straight for a custom kit. Personally, I'd question the value of water cooling if you are looking at kits. People generally choose kits because they want a better cooling option but with the ease of air cooling. Forget it. Water cooling, for those who are looking at kits, will be disappointed. There is still some noise, there's more hassle than air cooling and spending hundreds of pounds on water cooling is not going to give you a computer that peforms better if you spent hundreds of pounds intelligently in a different area. Regarding leaks and other problems, well, they don't happen if you do your research and take your time. Both of these factors are not prioritised by those looking at water cooling as an easy option of getting bang for buck, as opposed what you really get (mostly bragging rights, but yes, a quieter system and improved overclocking depending on your setup).
When people initially water cooled (before kits or even customised items) the word 'hassle' never came into it. Yes, they were doing it because they wanted to get more out of their components, but mainly to see what was possible. I have tried water cooling purely to see what was possible for me. I don't think it was worth it performance-wise, but as matt100 says, my next PC will also be water cooled using the same rad, res and pump (the most expensive bits for water cooling if you are going high end, i.e thermochill PA120.3). What I am most likely going to get more of from my water cooled system than if I was to air cool it is pride. That to me is worth a few quid. Just ask those that spend thousands modding their cars. It's not important to everyone, i.e those who see a computer as a tool, but to those whose sad little lives have been touched by the inners of a PC (I admit it!), it's important.
Oh, and for the record, I drive a Ford Focus and don't really care about cars so long as they work.
