Just came across a great post that goes into some excellent detail about using WordPress as a CMS. It goes into some detail about how you should use Pages and Posts for this purpose but the gem is the checklist at the end. Here’s the advice:

• Is there even a need for a CMS for the client?
• Is WordPress the correct CMS? Will it fit the needs? Is the translations available for the WordPress backend good enough? How will it be upgraded?
• Will I need to extend WordPress using plugins? Are any hacks to the core necessary, because if they are, how will I make sure that these won’t break when the core is upgraded?
• What types of content will there be, and what should be deemed static (i.e. use Pages), and what is flowing updates (i.e. Posts)? How will I present this, and what is the main type of content?
• How will the permalink structure be? Should it really say “category”, why not “view” or “updates” or something else?
• Will the menu be static (i.e. coded into the theme) or controlled by WordPress (i.e. listing using WordPress tags for Pages and categories)? How could this go wrong in the future?
• What hierarchy will the Pages have? This is important for the URL, since it should be coherent with the menu hierarchy after all.
• How will I present sub-pages (i.e. Pages having a mother Page)? Should there be any at all?
• Do I need Page templates for various sections? How will these work with sub-pages?
• What categories will I use? Should the client be allowed to create new categories?
• How will I present Posts content?
• Do I need category templates for the various categories?

It’s a great checklist to work through and can help you structure what you’re about to do. A number of blogs are echoing how successful they’ve been using WordPress in this way, though really it should be a tool you consider rather than jumping straight into it.