An extremely common complaint about Haskell coming from other languages is the proliferation of un-Googleable operators and symbols. I would be unhappy to see these changes made, especially as the fancy brackets aren't valid code (and thus can't be Hoogled or copy/pasted). I suspect that every non-maintainer of the containers documentation would need to look these symbols up every time they consulted the documentation, as the documentation would likely be the only place they're used.
The `fromList` calls are perhaps a little noisy -- having literal syntax like Python's for maps and sets would be nice, but that's probably not going to fly given that `containers` isn't part of `base` or the Report.