Late 2011 for me on my third attempt to get into it. I had actually been turned onto it in mid 2010, around the first appearance of Karkat, because he was instantly popular with a group of acquaintances at the time. I wasn't sure what I was even looking at at first, and only got a handful of pages in the second time. That third attempt tho I managed to overcome the "learning curve" and get on it's wave length and it just clicked for me ever since.