I haven't used FW much, but I've used AmigaWriter 2.2 and Wordworth7 a good bit.
AmigaWriter is ok, but not great. As mentioned above it has a somewhat awkward interface, though you'll get used to it. I'd say the biggest advantage is TrueType font support (with antialiasing). It can also import MS-Word documents, but only older versions (Word 97 I seem to remember?). I first used it on a A1200 with a 68030/50MHz. This was pretty slow. Now I'm using it on a A4000 with 68060/50MHz, and performance is quite acceptable. If you do get AmigaWriter make sure you install the latest patch, it fixes most of the bugs.
Generally speaking I think I'd prefer Wordworth. It has a lot more features, and it's more enjoyable to work with.
