The documentation is ok... there's a lot to wade through, but there's enough to figure out what you need to do. There are examples buried in a lot of documentation. You may need to experiment a bit, but it's easy to get the hang of.
It's pretty easy to use, and the interface is good (not excellent, just good). (I'm told it doesn't support all of SOAP's features, but it's handled what I've needed.)
The main limitations are in the SOAP protocol itself. There's so much overhead in bandwidth and processing (most of the data is just XML markup that isn't needed) that you're better off using something else. (Not a slight on the module, but on the protocol.)