I'm still feeling bitter after seeing it introduced on my last project, a Rails app. Build times went from seconds to 15 minutes. After experiencing that I will make every effort to argue against it's inclusion on my current project (should anyone propose it).
We tried to replace Gulp with it at work for some relatively complex software but it was an absolute nightmare; Webpack is highly opinionated and to get it to build multiple different targets with different configurations requires jumping through a lot of hoops or worse, having to have separate Webpack configs and different build commands for each different asset target.
The last straw for us was how messy it got trying to build our LESS at the same time. Packaging all the LESS into your compiled JS, then having to extract it to put it in other files is absolutely ridiculous.
This is what I'm trying to do at the moment -- create a static site that's just a bunch of HTML files, while still taking advantage of Sass, CSS modules, and Vue.js components. (God, I love scoped CSS so much.) I'm sure there's a way to get Webpack to do what I want, but I haven't found it yet. prerender-spa-plugin has been a huge help, though.
It seems very similar to when I was learning Git: I know what I want to do, but Git's interface uses a level one layer lower than the one I'm operating on. "Undo the last commit", not "Reset the working tree to the previous commit's, but leave the staging area intact". Webpack's interface seems too abstract for what I want. I want to think in terms of individual pages, not of entry points; components, rather than chunks. Hopefully in five years when flat HTML files are vogue again there'll be a friendlier interface on top of it all.
Edit: I don't mean to be 100% negative in my comment! Webpack has certainly helped me solve problems that, previously, I haven't been able to solve. That alone is great. I just wish it'll go "click" so I can "get" it.
Contributions welcome!