Operational content - ticketing systems

NANOG, We're looking to engineer a new ticketing system for our NOC. I know that several of you have had good experience with Request Tracker and Keystone; i'd like comments from people who are using other open-source systems (i'm not interested in Remedy). Particularly, i'm wondering if anyone's using GNATS or Jitterbug for tracking of this sort, and if so, what kind of modifications you've had to make to interface it to the rest of your stuff. Please respond privately in order to clear the way for WTC terrorist traffic, and i'll summarize later to the list after all the fury has died down. Thanks, Tim