i have same problem with iamdave007 about User Search on ticket creation form/change user of the ticket
in the OS Ticket v.1.9.12 we can search by user name, but in v1.10 have to inpu email_id.
Name of user : David Aliando with email id : email@example.com.
when we want to search that name on ticket creation form/change user of the ticket (Os Tiket v.1.10), we have to type "daliando@" than the user list appear " David Aliando ". in the OS Ticket v.1.9.19, we just type "david" it will appear drop down list with the first name david.