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.
As someone who's done his fair share of ExpressionEngine development, the template system is a source of endless frustration as soon as you need to do anything remotely complex on the page or deal with user input. It is a great choice for blogging sites where a group of editors publish content to a site in predefined channels, but really falls down if you push it too hard.
Template processing is slow, processing order is wonky, and it's very easy to create N+1 query loops that can only be avoided by writing custom SQL queries/php. They also made some poor database structure choices in certain areas.
Mostly though it just boggles the mind why they put so much effort into creating a regex-based templating system when the app is already just PHP.
Still, probably the best CMS I've used and it certainly has its uses. I just wouldn't use it to develop anything complicated ever again.
Sorry for the confusion - I meant to say "from WordPress to ExpressionEngine" on the first line... I don't know how to edit a post, so I'm just replying here.
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