I use Scrivener and am immensely happy with it.
Writers are all over the map with what software they use, but I am not convinced Word is well suited to the task.
Most anything can work.
I'll probably end up getting Scrivener when I'm ready to start actually writing and not just focused on researching and resource gathering.
If you are thinking of taking that plunge anyhow... consider that it's also a good program for keeping track of your research... I've got photos stored for locales that "inspire" description for writing in the book. That way you can stick research and ideas you know you'll use into the program so when you start writing, you won't have any downtime transferring stuff into it... if you would use it for such things, of course.