If you want to get your thoughts out there for people to read if they want, that's the perfect place. It'll give you a persistent bit of storage for your posts and maybe let you see how you change over time. It'll be a benefit to you even if no-one else reads it. It'll let you talk about whatever you want whenever you want. No-one will care if you flip into stream-of-consciousness mode for page after page. That's what a diary is for in many cases. :-)

If you want to participate in back-and-forth discussions with people, you need to find a discussion board where you fit in with the people there or you need to find a board where you can stay on topic. Have you tried USENET recently? There are thousands of places where you can have detailed, focused discussion if you want (e.g. soc.support.depression or microsoft.public.vb.general.discussion) or catch-all general discussions that are all over the map (and occasional dumping places for OT rants e.g. misc.misc, talk.bizarre).

I'd recommend your K5 diary myself. Just exercise some appropriate restraint and you'll be fine anywhere (even here).

My $0.02.

Cheers,
Scott.