When comparing virtualization to the use of a physical system and while they both have their inherent dangers nonetheless virtualization is inherently more dangerous and as such one must be more vigilant in backing up user data and additionally backing up the virtual machines themselves and being prepared to recover from a catastrophic event. In either case if you're not properly prepared to recover it won't matter which virtualization product you're using or what physical machine you're using or what operating systems you're using.
While many of us will experience similar faults not all of us will experience some of the faults others have and while I have never experienced a kernel panic under Parallels I have under Fusion however if I recall correctly I lost nothing more than what I was working on at that moment and rebooted of the Host and Fusion and the Virtual Machine I was working in started without further issue.
For what it's worth, in general, I prefer VMware products to Parallel products and use several other VMware products on both Windows and Linux platforms and I'm hoping that when Fusion 3.0 gets here it is everything Fusion should've been in the first place, although I be sure not to have any unrealistic expectations. 
