I generally am a bit of a purist with regards to hierarchical design. Possibly because of my software engineering background. For me a hierarchical sheet is just an object with a defined interface.
Global labels which include power symbols do not really fit this view for me. They introduce knowledge dependencies to something outside the current scope (so outside the current sheet).
I do also not see an issue with placing the same label multiple times inside a sheet. I would however wish there was a hierarchical pin type for “power pin” or possibly even a way to have custom shapes like we have for power symbols (but distinct enough to easily differentiate them from global power symbols).
I am excited about the new bus features that come with version 6. These will make my workflow even cleaner. (will allow similar schematics to how some FPGA programming tools look like)
For the interested i have written up my general view of things over on the kicad forum FAQ: https://forum.kicad.info/t/hierarchical-or-flat-schematic-design-what-is-best-for-me-how-to-deal-with-multi-page-schematics/16477