I think people also forget another fact - O(f(N)) means O(N) + c and a lot of times the value of c overwhelms the gains from algorithm for one off uses. O(f(N)

I think people also forget another fact - O(f(N)) means O(N) + c and a lot of times the value of c overwhelms the gains from algorithm for one off uses. O(f(N)) might also be amortized cost and you need to evaluate your use carefully to see if you see the gain.