Final Draft 8 is largely identical to FD7, with some better chrome. If you’re happy with FD7, the addition of a fairly useful navigator and a new XML file format may or may not be enough reason to upgrade.
I’ve been using it for a week, and so far, no crashes. There are a few quirks — awkward colorization during drag-and-drop, click-lag when editing summaries — but nothing approaching the bugginess of early FD7. It feels stable and looks like a 2009 application.
I’m not endorsing Final Draft or any of its competitors; each has its strengths and weaknesses. I’ve ping-ponged between Final Draft and Screenwriter over the years, but given its interface improvements, I’ll probably stick with Final Draft for a bit. Some of that is familiarity, frankly, particularly with how it handles production drafts.
There’s a demo version available at the company site, which is worth checking out.
If you’re upgrading ($79), the mechanism for checking your current license is a bit slow. If you’re buying it new, note that it’s $50 cheaper on Amazon.