(Thought I already posted in this thread... Apparently not, since 90% of its posts are from before I joined.)
September 2008. That was a couple months after I joined KIExtreme, which, for me, is now a mausoleum of my most embarrassing posts ever. (I used the word "n00b," complete with both zeroes, so, so many times... So embarrassing, haha. I'm sure a couple posts of mine were SH0Xing--right, ahank? )
I will say this much for KIC: even though I was never around for PKIU, etc., which many of you seem to consider the glory days of the site, this place has more or less consistently remained one of the best park/coaster fansites around. It's had its rough moments, but it always seems to work out in the end. There aren't unreasonable forum rules, disrespect for the park and its rules, or an epidemic of know-it-all attitudes like several sites I could mention. Trust me, I've shopped around to see what's out there.
(TL;DR: GROUP HUG.)