Another vote for Liberium here, we have been using here at our school (110 staff, 400+ machines, 4 techies etc etc) since the begining of the new term, 300 and odd jobs into its infancy and everyone thinks it's a great peice of software, the staff love the idea of being able to see their submitted job's progress, they say there is more interaction with our technical staff and they don't have to go looking for a technician or send kids out of class on a man hunt.
just my 2p worth