Reading this article, I got a bit bothered.

I agree with the sentiment: people repeat entirely too much code. There are very few cases where a for-loop is the right thing to write. Using generic methods which can be tested and shipped in isolation is basically always better.

But the article seems to imply there are performance concerns in some cases with its talk of using "a data structure". This irked me, because it's not like Set will beat linear time in balanced read-writes and without care the hash tables end up being non-constant as well.