An alternative that is not as well known is ExpressionEngine. FWIW, we've done a slew of EE installs and a few WordPress intalls and clients that have made the switch from EE to WP have loved it. The admin UI is attractive for end users, and when it comes to theming, designers love the flexibility of the layout variations and front-end developers can actually implement said designs without hacking the EE theming system. This is definitely not the case with WordPress.
Here is a great blog post about the transition from WP to EE written by one of our designers - http://www.viget.com/inspire/wordpress-to-expressionengine/
and here is another unique EE site that shows the flexibility of its native theming system -
www.teamviget.com