Celtic Heroes

I regularly check the AH and use my 5 slots all the time, I was wondering as I cannot seem to always find what I need do enough use the AH?

I remember back in the day when RS introduced the system similar to the AH is was great no more going to world one to try and sell or buy stuff. This is a great idea but I was wondering what everyone else thought and how many people actually use it to sell/buy.