Im quite a heavy user, i work in graphic prepress so im quite aware of issues that can arise on complex configurations. I also use Google drive, have a few shared drives and im connected to a fairly complex LAN for a home network. I admit i only have three email accounts setup in mail but it runs perfectly. I do alot of work in the adobe suite as that is my profession. I also bootcamp into Windows 7 on both machines. I also have over 6 TB's of files on my NAS and finder shows the directory contents almost instantly every time.
Im sorry but perhaps you should try a fresh re-install, if that does not work move back to ML.
Thanks Torana, but I'm NOT going through another clean install again. It's got to be Mavericks.