In my very humble opinion, water cooling is only worth the cost if it is absolutely necessary. Air cooling can probably take care of most of your temperature issues. Unless you are planning on overclocking you most likely don't need water cooling.
Another thing to consider is it worth your time to install? And you have to change the water every 5 or 6 months....also faulty hose could ruin your machine. It's one of those things where it's really only worth it if you REALLY need it. At least I think so.
I agree, good cable management, good fans/heatsink, all facilitate good airflow which is for the most part, all you will need unless you are doing some serious overclocking, It isn't worth it otherwise.
The majority of computers these days will be just fine with fans. I would not wait the extra money, and I would prob worry more with a water cooled system anyways.
Water cooling > Air cooling , most casses dont have enough fans to be able to properly cool every component inside the case and dust is no longer a problem with water cooling so yes it is very worth the cost.
How much money do you have burning a hole in your pocket is the real answer to if it's worth your while.
The big difference you will see in liquid cooling your pc is that it will be much more quiet and stay at a stable temperature much lower than with air cooling when you overclock. It can look cool and be afun little project. Even if you don't go all overboard like this guy: http://www.guru3d.com/article/guru3d-rig-of-the-mo...
Not really, parts these days generally run really cool. 3 of my case fans don't even work, and I can still keep my gpu and cpu overclocked at safe temps.
If you plan to spend the $200 vs the better hardware and some good fans, then thats your choice. I wouldn't water cool because my overclock runs pretty cool with a good CPU heatsink with a fan as well as exposing my GPU's heatsink so the house fan I attached ($20) can blow air through it. I used a fine screen to keep dust out of my case because I have a side exposed. I then have exhaust fans (2 top,1 by hard drive bay, and a fan on the back side of my CPU because i had an extra one this I thought would have no effect but I saw an average of 2 deg drop from this which blew me away.)
Water cooling is really for complex computing or things that 90% of people with computers really would never do or even come in contact with.
$20 box fan, ($30)3-120 mm fans, ($10)2-40mm fans are the easiest thing to obtain from scavenging. Heat sinks are key get a good one!