Which version should I use?

I was unable to glean more than bits and drabs from an admittedly quick scan of the forum, so I'm posting this here in search of an answer and so search engines can find this answer too.

Which version of Cog should we be using?

As I understand there are two versions:

  0.07
  0.08

three feeds per version:

  Stable
  Unstable
  Nightly

and two OSes which have compatibility issues:

  10.4.X
  10.5.X

We can't use 0.07 with 10.5, and shouldn't use 0.08 with 10.4.

Do I have this right? If not, what did I miss or get wrong? Thanks in advance.