At this point #get_pipeline and #pay should be fairly well tested. I
have used these calls personally, and I believe that others on this
list are using them as well. The other areas of the API could use some
love/use, but I can't really say which ones in particular need the
attention.
The most neglected area is probably the specs. They have been a bit of
a challenge to write since Amazon hasn't released full examples with
requests and responses for each API call. If you could either look
again in the FPS documentation and forums to see if this has changed
since the last time I checked, or develop your own set of requests and
responses that would be very much appreciated.
Other than that my suggestion for you is to jump in and play around.
If you find any bugs or missing features let us know and we can work
to get those fixed/implemented.
Let us know how it goes. Remit will really benefit from a broader user
base using a broader set of its features. I hope that you find that it
fits your needs well.
Tyler