Basically you get multiple snapshots, clones, record and replay and a bunch of other advanced features.
If you're an end user just looking to virtualize an OS, then you won't gain any benefit and there are plenty of free products that will meet your need. Virtualization has become a commodity product (Virtual PC, Virtualbox, VMware Player, and so on) - VMware is just keeping up with the other free offerings.
However, if you're doing software development, QA, etc. then you'll take advantage of the additional features found in VMware Workstation - Put it this way... ask your boss... "want me to wait around and waste time for a few hours a week, or will you shell out $190 for a Workstation license?"