I have the tab open daily and when I have time I also skim my feed a couple of times a day. Sometimes that or less is what I do for a week or two, sometimes there are topics that really spark my interest and then I read/comment on 2-3 or more threads a day for a couple of days. I'm not really making myself contribute just for the sake of it, which makes me a sinus wave user :D
Regarding the favorite thing I have to join c_hawkthorne and say the people. The people, and obviously the discussions that come out of it. In every discussion you will have a lot of profound opinions with arguments and quite often with that a nice debate. If I want to take people more seriously and read something else than the easily digestible stuff I'm reading most of the day, I'm coming here.
And I'm with you regarding the spelling: The faq writes it Hubski, but I also prefer hubski, just because it looks better imho.