It all depends on how you want to use VMWare.
If you're an IT guy in a company that houses a lot of servers and you want to virtualize them, then VMWare is a great product. You will need to purchase a powerhouse server to run multiple VMs simultaneously. I've got HP DL585 servers here with 64GB of ram. Each of them run 12 virtual machines. You will also need a SAN. EMC is not as good as some others. I prefer Equallogic. Dell just recently bought them out and their hardware/configuration is second to none in my opinion. VMWare also has lots of helpful tools that make things easier. Their VM Converter has been flawless so far. I've converted over 20 Windows Servers to VMs in the last few months and everything's working just fine
On the other hand, if you're thinking of doing something at home, then you might want to look into the VMWare Workstation product to play around with OSes. There are several open source alternatives that you might want to give a shot. However, if you plan on purchasing a virtualization product... I recommend VMWare and VMWare only. Virtuozzo and others and not as up to par and stability is always a concern.
Hope that helps.