Liquid cooling is verry good, much better then fans.
When we are talking about loosing heat.
It only is usefull for when you want to experiment with overklocking cpu, vga, ...
But, for a normal system without overklocking, it works just as fine as fans.
It isn't going to make your pc faster, and it takes more maintainance then a normal computer.
So I would say, don't do it if you don't know much of computers and aren't going to overklock.
And, it is verry expensive! For a full set you need at least €200!
You need a pump, reservoir, radiator, fan and cooling elements (for cpu, vga, northbridge and maybe even memory)