It is a vague question because the answer will be influenced by the number of users, how fast they operate, the style of application, does it open lots of windows, does it contain lots of uncachable images, does it use dialogtouched. etc etc
What I would suggest is if you are concerned about a bottleneck in that area is that you trial GDC, as its architecture means that less bytes travel backwards and forwards between back end server and the GUI client
