I'm somewhat of a new mac user, so I can't speak historically, but I will say that lion was quite a downgrade. It broke things that were previously working fine (my network drivers and my dev tools), removed useful features (rosetta), and really didn't add anything new that I care about. I never use the app store; I dislike mission control; really the only thing I actually like is the better window resizing.
My first impression after using Linux as my primary OS for the last ten plus years is OS X is very Linux-like in behaviour.
But I feel like I am in a glossy, trendy prison with a guard constantly next to me. Everything works well because it was all made by Apple or at least with hardware it was hand-picked by Apple to work with their OS. If Linux or Windows made a computer and the hardware was specifically hand-picked for each OS version I'm sure it also would run as smooth and be as glossy as OS X.
Rebooting after software updates was alien to me (use Ksplice on Linux) but I figured OS X was BSD/Unix based and never expected so many reboots for simple things.
I never use the App store either because I don't see why I need to enter my credit card information to update a free app.
Plus the lack of real separate delete and backspace keys is driving me crazy! (yes I know fn+delete is Win/Linux "delete")