When working in the Sales Cloud and writing reports, you have access to any custom fields that you created on the user record so that you can include them in your reports. However, this is not true for the Service Cloud!
This shortcoming appears to be due to Cases being able to be owned by either a User or a Queue, and thus this may be a hard idea to implement, however I believe it really important to have access to these fields for many customers. I know it is for my current customer. If you agree, please vote!