I don't feel as though I have right now, no. Which is a depressing thing to admit, as I just turned 25.
Last year, I would have probably said yes. I had a full-time job I was happy with, I was contributing to the household, and the way I felt and was treated was definitely different to how I was treated when I was in University the year before. I hadn't moved out - although I was looking at places whilst building up a small amount of capital; I would have definitely moved out by this point - but I was living a fairly comfortable life.
Now though, I've since had all of that taken away from me (quite literally, as health services have told me that I need to focus on recovery and shouldn't work until they say otherwise) and I'm dependant on my parents again; I feel like I've taken several giant steps backwards. I can still take care of myself - cooking and cleaning etc isn't an issue; I also frequently do household chores and anything else I can to make life easier - but I'm still financially dependant on my parents again, and I've lost a lot of the freedom I had before.
I'm at something of a loss at the moment, and whilst I would hope my reaction and how I'm coping with it is fairly adult, I still feel that if I really WAS grown up, I wouldn't even be in this situation in the first place. I would never have let myself get to this point (however I even got to this point...) and I would have overcome it much more quickly, instead of still being stuck in this position after a frustrating year of trying to get out of it and back to where I was before.
I've never really stopped to consider myself an adult though, I've never thought it to be all that...relevant, really. It's a difficult thing to define really, as it varies from person to person...I know some people twice my age who would definitely qualify as adults who act like children, and some people several years younger than me who are very mature...or, at least, more mature than I was when I was their age.