All of Swing's repainting architecture funnels into an invokeLater. This results in the event being processed at NORM_PRIORITY. AWT's painting/updating is processed at LOW_PRIORITY. If the machine is bogged down this can result in odd behavior when heavy weights need to repaint (swing can end painting its components numerous times before the awt one is painted, try java 2d demo), as well as not being responsive to the user. There needs to be some mechanism for Swing apps to post events at a lower priority (revalidate is handled in a similar manner and should probably be processed at a lower priority too).
I'm not sure if adding a priority to invokeLater fits in with the current architecture. Another option may be to expose a new event class for this sort of thing, that way awt isn't tied to the current priorities that are defined.