I was using VirtualBox on OS X and moved to VMWare recently. I was disapointed by the extremely slow boot time of Windows Server 2008 guest system (while XP booted fast).
I converted the VirtualBox images using kju-app tools and upgraded the image format when VMWare Fusion asked me to. I later found out, that when downgraded, it works as expected.
Since this has been known for quite some time (at least based on the release notes), it is strage it is not fixed. I am using Fusion 2.0.1.