I'd have to go for:
~ Community ~
Yes, yes, I know it sounds mushy, especially coming from a guy, but any site without community is just HTML.
I've visited many other sites, some with much much more content and information, but it's the people & community that keeps bringing me back to everythingtreo.com's forums.
I could rant more, but I'll keep it short. :tongue:
EDIT:
Also, Chris, THANK YOU for running/keeping up with this site.
You donate your time/bandwidth, which is greatly appreciated.
I know first hand how much time/effort it can take.
[hmmm...i use the '/' a lot...weird...anyways...]