Is it safe to upgrade to Leopard yet?

The instability in Parallels (5160/Tiger) only starts when you are using multiple VMs at the same time. I don't think I've ever had XP crash out on me when it was open on its own but it happens quite often when more than one VM is open. Then I'll do something and suddenly both Parallels and Windows are just gone, in a fraction of a second. This is "annoying" to say the least... (And yes, I have plenty of memory: 4GB on the MacBook Pro, 5GB on the Mac Pro.)