> I really don't think its such a great idea to reinvent the UI wheel, throwing the decades of research and refinement represented by native UI toolkits under the bus for the sake of branding and aesthetics, unless you have a good reason

It's a romantic thought, but that boat sailed a long time ago. Users got used to the web that had a very inconsistent UI between websites and on the website over time; before bootstrap, you would be hardpressed to find 2 websites with the same button styling. The last time the web used unstyled OS-controls was the 90s (with that default grey background - blech).