I just finished up a GTP client for KGS. With it, any GTP go engine can connect to KGS and play there. This has been a problem for KGS for a long time - one of the big advantages that IGS and NNGS have with their open protocol is of course that people could easily write a GTP (or any other kind of client for it). Now that I've finally written the GTP client for KGS, I wish I'd done it sooner - it was much easier than I'd expected.
I've been using GnuGo to test with. About 20 games have been played in the past 24 hours, so it seems that the major bugs are gone. I have not tested with any other engine, so problems may show up due to small variations in the way that GTP is used.
If you have a GTP go engine, please go to http://www.igoweb.org/~wms/upload/ and try downloading it. I'd be really interested in what people think of it.