For everyone complaining about the flatness, it looks like it's only temporary.
https://github.com/twitter/bootstrap/pull/6342#issuecomment-...
https://github.com/twitter/bootstrap/pull/6342#issuecomment-...
Customizing Bootstrap has always been a pain (and I'm not the only one to think this, in the words of @mdo : those who want to use Bootstrap as a bootstrap kind of get the short end of the stick), I'm very happy to see that they're looking to make this easier.