Recently updated to 12.04 (64-bit) on my AMD hex-core 4GB system, over the last few days I feel that the overall system is sluggish/laggy, for instance hitting the dash button, the dash opens but the recent activity of files/videos etc is incredibly slow to populate, like wise in Nautilus and browsing my media, the file names are showing up but it takes an age to populate the "thumb" of the video, If I go into Gnome-shell the shell response is a little faster but again clicking on applications there is still a noticeable pause.

I have the latest Nvidia drivers loaded and I have very fast SATA drives, if I reboot into windows 7 the system is so much quicker in its response, I only use windows for games and Ubuntu is my main OS.

10.04/10.10/11.04 was super quick and this was when the system still had a dual-core Chip and a worse Nvidia card, 11.10 was pretty snappy, but 12.04 just feels bloated on each system I have installed it on.
My hardware is more than up to the task so has anyone got any commands i can run to help diagnose the issue?

Anyone else got the same problems?