I find that one of the biggest differences is the file ownership/group design, and the non admin user. Sure, it might not come up in a straightforward manner, but it will.
Why do I need to put in a password all the time? How come I can't just move this file to another drive?
This might be too "advanced" for what you're looking for, but I think even basic usage comes across this.
Yeah, I always bring this up because it's what I dealt with. Mind you, it was amplified because I set up a media server right away and got seriously confused.
What? Permissions don't get inherited? OK fine, so how do you set permissions? This site says 755 and this site says drwxr-xr-x. Can't I just get a straight answer?
It's a fundamental functioning difference between the OS's that not a lot of people talk about when talking about switching.
Even my Windows machine that is set up with an admin/user structure (as God intended) doesn't give me any fuss with file access.