Either way, it's your chance to make a difference!
Yes, they have. Don't confuse usability with the software having an interface you haven't gotten used to yet.
Free software is a docracy, so if you are the expert in usability step forward and make it better.
Some did, some didn't.
Fake it till you make it.
What's not usable, moving from win-dust to OS X has a curve, same thing this way round.
Do you want to help improve it?
Have you ever considered to learn another usability?