Re: TikiWiki 3.0 - upgrade and new install
I think category paths didn't get much attention in Tiki 3.0, maybe just enough to get by, so it'd good to take another look at them. If you can be more specific about the problems here, that'd be helpful.
About the ads, a problem is that site header area is fairly compact so conflicts are likely, depending on what's activated. It might be necessary to choose between displaying a banner ad and having the site header login form activated. An alternative to this login form is to use the login module instead. Or in a particular theme it might be possible to nudge things around in the site header for a better fit, so if there's a particular theme where this seems possible, let me know and I'll see about improving it.
IIRC, there was a bug in the "Discuss" function for wiki pages in Tiki 3.0, but it's fixed in 3.1, which is coming soon.
You could submit a feature request, at dev.tikiwiki.org, about associating a forum with a category.
-- Gary