I have used Mr Yap several times...
Seriously..... I cannot even find the spot again.
Of course if you inspect it with a find tooth comb, you may be able to spot it, but generally...
Totally satisfied!
Tried the dry ice method once and it didnt work. It seems to appear to have made the dent less obvious initially but after a few minutes, the dent is back to waht it was earlier. I concluded that it is an urban legend.