There's really no need to sell Underscores in its README.me file. That's what Underscores.me is for, and it's already tedious enough to keep the website up-to-date.
Let's refresh it.
Suggestions for what the file should include are most welcome; commits or pull requests aren't really needed at this time.
I think keeping the "Getting Started" instructions in the readme is important, that's traditional "readme" material, but almost everything before that could be removed. Maybe keep the first introductory sentence (warning users not to use it as a parent theme) then link to underscores.me and/or Github for further information.
Closing. We think that it's not a bad idea to sell Underscores in its README.md for users that come straight to GitHub and don't click through to Underscores.me