Just how bad is not running PHP as CGI?

I run quite a few WordPress blogs on various domains all hosted with Dreamhost. For a couple of them I no longer run ‘PHP as CGI’ because it prevents a plugin/functionality I really want to use from working.

Other than initial CHMOD problems when I change an existing blog to run PHP regularly, everything works great.

Can someone tell me what to be wary of (permissions-wise)? I’ve tried to CHMOD my files as conservatively as possible but a few need to be writable by group, most need to be executable but not writable by all.