The buglist for gtkeyboard is provided through GNU at bug-gtkeyboard@gnu.org for your enlightenment. It is a currently a mail alias, but may be a list in the future. Send all bug reports there. You will find a list of known bugs in the BUGS file in the main source directory. You may also send bug reports to s2mdalle@titan.vcu.edu
The current bugs in GTKeyboard are usually small cosmetic issues, and sometimes minor annoying things that I'm working on currently or are planned to be fixed. There aren't any major stability issues that I know of. If you find one, email the bug list and let us know.