Scrivener is a different type of word processor. It combines word processing and project management tools to make it especially userful for writing long texts and papers. It takes a bit of rethinking about what you expect out of a word processor.
There's a great honesty to the company, which is really endearing to a customer looking for an alternative to the Microsoft Word beheamouth. They know that the product isn't for everybody, and are very upfront about it:
Is Scrivener the right tool for you?
...Because Scrivener is about shaping chunks of text into a final typescript, Scrivener knows nothing of pages until it comes to exporting or printing and therefore does not have the page layout viewing features of modern word processor applications. So if you are just looking for an alternative to Word you might want to try Nisus Writer or Mellel. If you are drawn by Scrivener's full screen mode but aren't bothered about its large writing project management tools, try WriteRoom...
The old rules of never mentioning the competition (at least in a good light) don't apply here. They even go so far as to dedicate a page on their site espousing the benefits of a bunch of competing products.
Smartly, they reinforce the 30 day free trial of their own software in each of these places, so why not give it a try? It might just be right for you.