Lots of various bug fixes since alpha6.
If you are upgrading a subtheme already created, your style/scss/_style-vars.scss will need to be renamed to _omega-style-vars.scss.
There may be other issues upgrading. Please check the commit log for changes that may apply to you.
Always test with a newly created subtheme.
New subthemes exported can include a config.rb and Gemfile if they choose.