Found a new bug unfortunately although Spaces _might_ be the one responsible here...
When using Spaces together with the single-app/hide mode in FlyingWindows, something makes the cmd+tab-switcher to default regardless to Finder as the last used app.
This makes it necessary to keep pressing twice on tab, which defeats the possibility of a quick flick on cmd+tab to return to the last used app.
Although in regard to Spaces, disable FlyingWindows and everything is back to "normal" with the tab-switcher. i.e. quickly flick between the two last used apps.
Sorry if this is confusing...
yet so is figuring out why I kept ending up in Finder all the time without having the mouse cursor anywhere near the tab-switcher.
o/t, the tab-switcher feature is actually something that other OS does better as in OS X this feature is clearly "over-thought". As it is prominently a keyboard feature, Apple could at least give us the option of making it disregard the mouse but no. :/
For now it is either Spaces OR FlyingWindows. Thank you.