Over at the Emacs subreddit, meedstrom raises an interesting point: why is everyone hating on the Dash library? The short answer appears to be “dependencies”. Using the Dash library increases the number of dependencies and everyone knows that’s bad.
The slightly longer answer is that most of the Dash functions have—at least rough—analogs in the builtin libraries and thus using Dash increases the number of dependencies and everyone knows that’s bad.
I’m a huge fan of Magnar Sveen from his Emacs Rocks videos and other work on Emacs. I often find myself using his Dash library because its functions do just what I need doing in a simple way. That said, I’ve never once actually required the Dash library. That’s because it’s used by so many packages that it gets pulled in to just about every Emacs installation. Bad form, I know, but I don’t generally distribute my code so I never think to include Dash explicitly.
Increased dependencies or not, Dash is everywhere and no one that I know of has anything bad to say about its quality. So the argument against Dash boils down to: “Dependencies bad”. Meedstrom raises the heretical thought that maybe—at least in the case of Emacs—dependencies aren’t really a bad thing. He also notes that in order to get the same functionality you need not only the builtin libraries but another third party library (llama) anyway so the hating on Dash is really pointless.
You can read meedstrom’s post and decide for yourself but I find his argument convincing. In any event, Dash isn’t going anywhere so maybe all that negative energy should be redirected to a more deserving target such as … Well, you know.