But it's hard to use the existing version:
* they stop doing updates (bug fixes, security fixes, etc) on the existing version when they release a new one. And being a complex product, there are a lot of bugs to fix :)
* the existing versions don't work well with new OS X releases - Fusion reaches pretty deep into the OS, as I'm sure you know. I had to upgrade to Fusion 4 to make Lion work. Not sure yet about 4 on M.L.
The problem is Fusion is not really a mature product. It's a hard piece of SW to write, so the lack of maturity isn't really a problem by itself. It's just that they've effectively put me on a $50/yr SaaS plan without me realizing it.