Khue,
Its not really a big deal. A lot of the features of VC revolve around using hosts & storage as shared pools of resources. Currently you have a few small islands, where shipping components between them is slow and costly. However, depending on your business needs, that may be just fine. The addition of a SAN will bridge all those islands an open up many opportunities.
You miss out on features such as DRS, allowing Virtual Center to balance guest load across clusters of hosts. You also miss out on HA (high availability). But you still have a central location to view / manage your virtual infrastructure. You get the benefits of directory integrated authentication, roles, templates, resource monitoring, alerts, update management (though UM is somewhat hampered since host maintenance is difficult without a SAN), etc.
After only a few hosts w/ or w/o a SAN, VC provides plenty of benefits to justify its cost.
Regards, J
