silex-bootstrap is nothing more than Silex with some stuff already set up for you:
Template rendering with Twig
Database interface with Propel
Directory structure for your project
Silex Web Profiler
Functional test environment with Behat
Unit test environment with Atoum
A Silex application (which uses Propel, Silex Web Profiler, Behat and Atoum) | Heykuki News