Build a vCloud lab is interesting to increase your skill and knowledge, make some test and of course preparing for the VCAP-CIA exam. If you build on a ESXi nested environment you will not have too much problem (except with old hardware that may not support complete ESXi nesting with vSphere 5.1). With a VMware Workstation environment (of course with enough memory and resources) could be more fun and portable. But could be more difficult if you plan to use vCloud Director virtual appliance.