Fusion 4 now officially supports sound in OS X Lion guests; but sadly still not in (Snow) Leopard Server guests: I discovered this after making some quick experiments creating OS X virtual machines, where only in Lion VMs the audio device is created automatically (so other OS X variants still need the third party VMsvga2 audio drivers).
In Lion, sound is supported on the OS X side (Lion supports Intel HD audio natively: probably - but I'm not completely sure - with the AppleHDA.kext kernel extension): so, it doesn't seem to have anything to do with the VMware Tools (while, IIRC, in Parallels it is the Tools - installing kernel extensions - that provide sound for all supprted OS X variants).
Looking inside a Lion VM's .vmx file, there is indeed a sound.virtualDev = "hdaudio" line, which seems to confirm all this.
There is one problem, though: the sound isn't certainly perfect, and stutters with some form of "instruments" (for example, with the Glass system alert sound): so, there's still much to improve, here (besides still not having audio in pre-Lion guests)...
