Jom is a fantastic tool. However, sometimes ~(once every 200 runs) it will fail to exit which causes my build system to appear hung. When this happens the jom pid is still active but no instances of the compiler are running. When I check the logs all of my operations completed... but jom didn't exit.
I haven't had time yet to play with any code changes to see if I can make it worse or better.
Could still be related to
QTCREATORBUG-6805 (the fix for 6805 did drastically improve things).