My ears tear up when I hear French
and when I have to speak it my brain takes a coffee break but I did find it ok to learn, in the sense that it does have rules, no matter how convoluted they might be.
I recall sitting in French classes and the teacher would give a morphology rule and then fill the whiteboards with exceptions, lol. I guess that just contradicts the first paragraph.
Maianhvk, how about a language that changes gender from singular to plural (or it appears to do so anyway)?