I've looked into the transitions.ini and for now I haven't found a way to turn off this fade-in effect through this file alone.

There are some interesting values though:
[popup]
duration_in=250
duration_out=250
...

These two values control the speed of which the status menu and other menus appear and disappear. Setting them to '0' make them appear/disappear instantly, so both the fade-in and the fly-in effects are gone. That's not really pretty though but you can change the setting to something in between, so at least it makes these animations faster and snappier. It's not that perfect though because you can also clearly see that the blurring of the background still is processing, while the status menu already fully appeared.

So I'd be really happy if there would be a way to just remove the fade-in effect completely, so the fly-in animation remains.