I've used Microsoft Word in various incarnations for years. And it may not be designed for writing novels, but there are some features I've found very useful.
- Thesaurus. I use this for virtually every sentence. Add the Thesaurus button to your toolbar, or hold down Shift and F7, and up pops a list of synonyms.
- Word Count. You can have it displayed on your status bar or simply ask for the word count as you go along. That way you can set yourself writing goals. You can also highlight sections (say, the part you wrote today) and find out how many words are in that section.
- Track Changes. I don't use it much when I'm writing, but it's standard in the editing stages. Combined with comments, it enables you and your editor to easily work on your manuscript.
- Font colours. I use a code. Red means that a section of text is plot outlining which hasn't yet been written up. Blue is a sentence or section I'm not happy with and want to come back to.
- Cut, copy and paste - Ctrl X, C and V - are, of course, completely invaluable.
- Find and replace. Want to see all your chapter headings? Simply Find the word "Chapter". Want to change a character name? Just use "replace all". (Although it may be more sensible to go through them all individually. I once changed a character name from Jack to Steve and later found that he wore a Steveet and Steveed up his car to change the tyre.)
- Spellchecker. Of course. But it's not infallible, so you do still need to know the difference between your, you're and yore.