VMWare Fusion: awesome when it works but too fragile ...

I was very impressed by VMWare Fusion the first several days when I tried it.  But the more I use, the more I found that it's actually pretty fragile.  In the last several days, I already experienced some mysterious crash twice while using it in the middle of the process.  It also doesn't matter if I am in Single screen mode or the integration mode.  When it dies, it brings down the whole system, which is kind of lame to say the least.