As a developer, I would just like to add a few more reasons why wordpress is the dominating force in the blogosphere.

Pings and track backs

From wikipedia:

Track backs are used primarily to facilitate communication between blogs; if a blogger writes a new entry commenting on, or referring to, an entry found at another blog, and both blogging tools support the TrackBack protocol, then the commenting blogger can notify the other blog with a “TrackBack ping“; the receiving blog will typically display summaries of, and links to, all the commenting entries below the original entry. This allows for conversations spanning several blogs that readers can easily follow.

Compared to other blogging software out there, wordpress is the superior product to handle ping and trackbacks. Superior to expression engine, blogger and movable type. Why are ping and track backs so important? Exposure. the TrackBack protocol, as simple as it is, helps to give your article the depth and breath that it would not normally see if it were up to you or your community to forward on your blog topic.

Development Community

With wordpress leading the charge in the blogosphere as the number one platform to publish blogs, the development community has come with them. Need a plugin to manage your ads? Need a plugin to increase your SEO? Need a plugin to create sitemaps? All those are accomplished with a few clicks and a download. With such a large userbase and supporting development community, chances are that someone out there has had the same need as you and there is a solution available.

All this is not to say that the alternative platforms are not wonderful engines to create your blog, not by any means. However, if asked, I personally would reccomend using wordpress.