I've been using OSTicket for a few weeks, and for my needs it's almost perfect just the way it is. I've been suggesting it to clients as well, but unfortunately it misses the mark on a few important features that other kinds of businesses would benefit from. In most of these cases I think that if OSTicket supported a plugin API similar to CMS's such as Wordpress, it would make this process much easier.

These are a few I've been presented with of late:

1. Custom queries, where the user can pull a client's complete history easily by simply searching by name or company name. Other reports such as by location (state, city, store number, etc) would also be very handy.

2. Registration of specific client information including company. Often enough, the specific person/representative at a company will change but the client itself, the company, will not. It would behove the OSTicket user to be able to have that history accessible by company rather than by a specific email address or person's name.

3. Editing contact info by Company, so if as in the above example, the specific point of contact changes, it can be changed without losing access to the company's history.

4. Ability to specify a specific client as an Individual or as a Company, and sort accordingly.

5. Reports. I have a client who wants to use OSTicket, but who wants to be able to pull full reports for any given client, and possibly even print those into a nice pdf format.

Certainly there are other things to add, but these are the most recently asked of me, and it occurs to me that many of these kinds of functions could be easily added via plugins supported and created by the community, if such a system were made publicly available. As far as I know, no other ticket system supports community submitted plugins; it'd be great to see OSTicket be the first.