A friend of mine showed the game to me late 2011. Only times I played was when I visited his place. Didn't take much interest in osu! until I could start passing Hard difficulties my buddies couldn't beat.
I made my account March 3, 2012. It took me a few months before discovering the forums and community.
Haven't been able to get around to playing much as of the last few years but I still enjoy revisiting my old favorite maps.
My account here been registered since the beginning of 2016 but I didn't really catch what could I pay for do its been about one year useless. I really started playing on November of 2016 ( you can check it in the historical graph)
According to my profile page, I've been here since December of 2010. As for how much I've improved? I have no idea(though I would hope I've only improved). I took leave of osu! around 2012, then only stopped in every blue moon to see what was happening.
I've only just recently started playing maps with the intent to actually improve. Back when I first started I would only play the approved beatmaps with the occasional map I could actually pass thrown in so I never got better at the game, then eventually I just gave up. Plus my hard-drive crashed around the same time, losing all my stuff as well as windows, so I didn't really bother seriously trying to come back for the longest time.
I started playing Osu 2 weeks ago after a friend irl told me it was pretty neat back in April and I started playing on his account at his house like every weekend for about 5 months (which is back in April) until I finally replaced my dinosaur aged computer so I could play Osu and for how much I've improved I cant really tell because well lol my stats from 5 months ago aren't accessible because its on my friends account lol but recently I've gotten much better and I guess that's it lol