I've tried to use _s for a project and it was very bloated. This looks much better although what the generator only does is to rename the theme.<p>Hopefully this becomes the official starter theme with a much more powerful generator to support it.
I think that Toolbox (also from Automattic) is the best minimalist theme that you can use for building a theme from scratch.<p><a href="http://wordpress.org/extend/themes/toolbox" rel="nofollow">http://wordpress.org/extend/themes/toolbox</a>