VMWare Workstation is getting a much-needed upgrade soon that is likely to be in demand, with the new Workstation 6 supporting, among other things, Windows Vista. Whether as a host or a guest, 6.0 will support Vista, which can be a great benefit to developers or IT managers looking for a way to deploy Vista without disrupting their existing installations. They'll also be introducing support for multiple displays and offering the ACE Option Pack, which is really just a way of transferring configurations from one machine to another. I have found VMWare infinitely useful for running a lot of software that DOSBOX or Wine can't, or can't do accurately enough. One particularly interesting feature, which is still in development, is “record and play” :

Workstation 6 also features an experimental "record and play" function, which he said records the deployment of a virtual machine and allows a user to rewind to the start of the recording and replay the deployment to see where bugs might have occurred. This would be particularly beneficial in software development because a tester could see where problems developed, Phillips said.
VMWare currently holds the lion's share of the market when it comes to virtual environments, but they are facing some stiff competition. Microsoft offers VirtualPC for free and the Xen project has made a lot of progress in a short amount of time. The next few years, as virtualization picks up, will be interesting.