One of the first things to check is if you've got enough memory...(this is not the case for you , but oters might also benefit from your question)
Then did you give locate the scratch file in a different physiucal drive than the windows pagefile? At least try to locate it in another partition...
The file browser can slow down PhotoshopCS...
Don't simply shut it off, it is doing wonderful works for you, as it is way more powerful as it was in V7...
In the File browser's preferences: disabe HQ preview (only if you don't use it) disable background processing, and launch a complete indexing of your hard drives during one night?
Also, Photoshop CS is now using bigger Tiles (the memory blocks in which he stores any info) So if you've got a lot of presets, they might take more space, especially if you've got a lot of memory (their size is dynamic) ...do not think it is sloppy programming, they had to do so with the sub-sub-sub(etc) layer sets that requires a lot of memory overhead...
Make sure that PS lets some memory for the system, do not set the memory setting to 99% (that is, unless you've got more than 2Gigas of memory) I've read that a good setting for the file cache is 6...
Another memory eater are instant messaging programs, and trashcan recovery programs (some even unhook their PS machine from the network and disable their Anti Virus' realtime protection)