There will always be some element of the user experience you can't control. What about the shape of tabs, or the colour of the [X] to close the window? I think

There will always be some element of the user experience you can't control. What about the shape of tabs, or the colour of the [X] to close the window? I think the scroll bar is in that category - it has nothing to do with branding and a browser scroll bar doesn't devalue any brand. I just checked and perhaps the biggest brand in the world - Coca Cola - uses the bog-standard scrollbar. So if it doesn't ruin their brand, it is probably OK for you too.