Adobe has just released a plugin to speed up the saving of large (>1GB) multi-layered 16bit PSD files in Photoshop CS5: http://kb2.adobe.com/cps/902/cpsid_90248.html

the following article details the plugin: http://macperformanceguide.com/Photo...ressedPSD.html

works for both Mac and Win Photoshop CS5... too bad only works for 16bit files... note also that the resultant saved files are also much larger... but the time savings are quite significant...