Walther, you are obviously a very nice guy with a lot of patience ad understanding. It is your prerogative to be as forgiving as you like, but it is still e-on's responsibility to provide a working program for the money they charge.
On their web site, in the company profile section they declare:
"E-on software's products are available worldwide ... for both Microsoft Windows and Apple Computer's Mac OS X platforms, making full use of the native software and hardware acceleration."

They dont say 'the mac version is inferior', it isnt cheaper, so why shouldnt customers expect the same performance?
I do appreciate that fixing bugs can be really hard, I've been a programmer myself, but it is no excuse. Either they can make a working product in which case they can take my money, or they cant in which case they shouldnt sell it (or fix it in a reasonable amount of time).
What other type of product would you accept under these conditions? I imagine its quite hard to make an appliance so that all mechanical and electronic parts work as specified, but you wouldnt accept a flawed appliance?

Couple of specific points-
-"The drop issue is one of those, probably because without noticing you clicked too long and therefore did a smart drop instead of the normal one."
I thought of that, but no it isnt, it happens when I use the keyboard shortcuts too, and those are very different - on the mac you need to press the ctrl key in addition in order to get the smart drop.
-What bugs did you report? it might help to know so that other users dont waste their time with them too.

"I paint that which comes from the imagination or from dreams, or from an unconscious drive. I photograph the things that I do not wish to paint, the things which already have an existence."
Man Ray, modernist painter
http://artpearl.redbubble.com/