In my experience the free stuff in with the Hyper 212's is just as good a the Arctic silver 5 but is non conductive. I have run both pates on the Hyper 212 and showed a +2°c with the Arctic Silver 5. Some thermal paste is better than others but usually the range is within less than 10°c difference between the worst and the best.
I will try to find the article Toms did on this subject and paste a link for you.
It is kind of worth it if you want the best possible temps and i have heard that the paste that comes with cooler master coolers isent too good.
Unless you have compared it to something, That statement is unfair. As i have in real world scenarios and found it to run about the middle of the pack or so for TIM.