There is a standard method of accessing Project Server data and Custom Fields information. That is create web service reference with PSI. Recently I have created a report of Projects with custom field values with some business requirements. Now, the the loading time of the report is very high and that is causing huge dissatisfaction.
After some searching I found a Project Server database view, which contains all the project information with custom fields values. The name of the view is MSP_EpmProject_UserView and it is present in Reporting DB.
Once you are able to find the view, then you can write query according to your needs.
Cheers,
Somu
