Point is made as how Howler is not effective as a trap that forces the runner to encounter ICE and suffer damage. But I feel that's the wrong way to think about this card. This is an HB trap we're talking about, not Jinteki.
This is how I plan to use this card: Say I'm trying to score an agenda while very low on credits. The runner feels confident that I can't rez anything that can keep her out so she runs the scoring server then boom surpise Wotan.
Then there's its use for recursion and delaying the decision of where to commit the only strong ICE you currently have ("if the runner doesn't contest my scoring attempt now, i'd best have this ICE protecting R&D while I dig for the next agenda").