tetsuo, are you using the Mac or PC version?
Also, are you talking about editing a CS3 document in CS4.
Have you re-created a similarly complex project in CS4 from scratch, is it just as slow then? I'm wondering if it's a migration issue, or that CS4 is just slow in general. It's funny, but I posted a similar thread in Kirupa and not many of them are complaining about speed, but I guess most of them do everything in code...
http://www.kirupa.com/forum/showthread.php?t=311761