But, if your pages are not related to
the "main" blog, why bother using
Wordpress?
- It's a well known plataform, tested and used by millions of people;
- A Huge plugin ecosystem that deals with SEO, Backup, Twitter, E-commerce, you name it;
- A great documentation;
- A great admin interface with WYSIWYG editors already implemented;
- An interesting approach to use "static pages" along with your posts, so you can have a full blown CMS application.
These are just some advantages. I don't recommend Wordpress for huge enterprise portals, but if you're not doing a complete different way of interaction (like stackoverflow, which is unique in it's way of work) for a website, I think it's a better approach then trying to code everything from scratch.
To write plugins you just use php, html and some functions aviable at plataform's core. No useless XML configuration files, no proprietary template languages inside the plataform, nothing. Write a bunch of php inside a directory, put inside "plugins" and you're done.