I've made the switch to the Workstation 6.0 beta on my main desktop now... it's totally awesome. Although I did find a few bugs, they are mostly minor or cosmetic (except for one really huge, massive one which I'll describe shortly). And sure the full debugging mode might have a little impact on performance, but not enough to make me care. The fact that I can use VNC to connect to VM's now (just by ticking a box in the VM's options - no software is required in the VM, not even VMware tools) saves some memory to compensate for that anyway - running a VM with the Workstation GUI uses around 23MB RAM and around 1% CPU per VM, whereas connecting to a VM via a VNC Viewer uses around 4MB RAM and pretty much 0% CPU. Since I usually run 3-4 VM's a time, that's a big benefit... even though I may need 4 VM's running, I rarely need more than 1 console displayed. Plus there's just something cool about watching a machine boot via a VNC window... that's right, since the VNC viewer is connecting to vmware-vmx.exe on the host rather than a VNC server in the guest, you get a proper console connection like an iLO on a HP server.
Then there's all the other numerous tweaks... mounting vmdk's from the GUI, the dual monitor support (bloody awesome)... it's going to be a truly great product. I don't care if Virtual PC 2007 is going to be free - like so many things in life, you get what you pay for! Although being a VCP, I do get Workstation for free anyway, but you know what I mean :-D
Now about that big nasty bug. If you take a snapshot of a VM, then add a pre-created virtual disk, then later revert to the snapshot... the vmdk file is deleted from disk!!!. I was expecting that the file would just be removed from the VM itself (ie removed from the .vmx file), so was quite surprised (and alarmed) to see the vmdk disappear from the filesystem. I have filed an SR with VMware (they use their support request system for bug tracking, oddly enough), and anyone reading this should do the same!