go make this UI with pure Win32 primitivesI happen to be both a demoscener and Win32 programmer, so I know exactly how to do those sorts of effects without bloat. That doesn't mean I necessarily advocate doing it, however.
It's ironic that you mention fancy progress bars, when the ones in the VS installer are even less fancy than the built-in OS ones. 2 colours, no 3D border, not even a gradient.
One of my annoyances is applications which reinvent standard OS controls and UI. The OS has (or unfortunately, more like had these days... but that's a different rant) theming and customisation capabilities for a reason. Don't try to be different just for the sake of being different, you'll stand out and not in a good way. It's an accessibility issue too: what happens when your custom-rendered UI is run on a system where the user has configured a custom colour palette (because he/she is colourblind, or just finds some colour combinations easier to use)? The OS UI widgets all have a consistent style and change all together, more than can be said of custom UIs.
(In applications like games, it often makes perfect sense to build a custom UI because it's part of the gameplay experience; but for a productivity application, a custom UI just gets in the way.)