I have a Windows 7 guest running in VirtualBox, which is hosted in Ubuntu 12.04. Both the operating systems are 32 bit.
Since the installation on Windows 7, the OS has been running very slow. I have been trying to figure out as to which component is resulting the in the slowdown. Initially the disk speed seemed to be the culprit, but on analysis it seems to be ok. Later I guessed that the 3D acceleration might be causing the problem, so I switched off 3D acceleration for the virtual machine, and bingo the speed problem was fixed.
So moral of the story: There is cost involved with all jazzy things.