I've been using Scrivener now for a couple of years and it's become my software of choice for writing new novels. So why is that you ask? Well, let me give you a few of the advantages of using Scrivener over using a product like Microsoft Word.
1. Moving text around in a novel - Editing a 50,000+ Word document is tough. First you have to find the part of the novel you want to move and then somehow you have to cut and paste the text to somewhere else. Sounds easy? In practice, not so much. In Scrivener it's easy. All you need to do is to find the index card that contains the scene and drag it somewhere else in the manuscripts. Done!
2. Finding a particular scene where character x does y because you need to refer back to it - We've all used search in Word. It's a long tedious process and it's made even harder because we have to then keep switching backward and forward between pieces of unrelated text. In Scrivener I can initiate a search and all the scenes that contain the reference I am looking for appear highlighted in the left column. I can then quickly quick between them. I can even have two of them open simultaneously in two different windows. Love it!
3. Trying to see the manuscript's big picture - What I mean by this is trying to see the synopsis and general story flow of the novel. Impossible with Microsoft Word. With Scrivener all the index cards have a one word sentence on them and can also be color-coded according to character, theme or place, etc. This makes it really easy to take the big picture look at the manuscripts and easily find a particular part of the storyline.
Scrivener is the best software for writing a novel. Period. And I haven't even touched on a myriad of other features it has. I would never turn away from it now. It holds my scenes, my character descriptions, my towns, by background research, my maps, my plots, my everything. All in one place that I can use wherever I am. If you haven't tried it yet - give it a go!