CloudSim is a adiscrete-event cloud simulator which is mostly suitable for simulating IaaS clouds  and cloud data centers. The good think about CloudSim is  that you can easily extend primary classes to create your own modelling and simulation of the desired cloud environments. There are couple of different extensions for  cloudSim for example cloudSim with Power usage modelling and CloudSim with Network modelling in a datacpneter.

 It provides basic classes for describing data centers, virtual machines, applications, users, computational resources, and policies for management of diverse parts of the system (e.g., scheduling and provisioning)  ref.  https://code.google.com/p/cloudsim/wiki/FAQ 

I come to think of it as more of a controller rather than simulator.

Yes, it performs under restricted conditions of existing scheduling algorithm and dynamics is missing.

Yes, you can create cloud computing environment with multiple data center and multiple users. It also helps to analyst many cloud computing functions such as energy consumption in DC, load balancing, data center networking and cost modeling etc. in a given scenario. You need to know Java, OOP concept to  use above simulators.

For me you can refer following material: 

Website: http://www.cloudbus.org/cloudsim/

Paper: http://www.buyya.com/papers/CloudSim2010.pdf

CloudSim is a simulator of Cloud Computing that enable repeatable and controllable environment free of cost, tune the performance bottlenecks before deploying on real Clouds. CoudSim propose: a new, generalized, and extensible simulation framework that enables seamless modeling, allowing that researchers and industry-based developers evolution their Cloud Computing infrastructure and application services.

Some characteristics are unique of CloudSim, such as, support for modeling and simulation of large scale Cloud Computing infrastructure, including data centers on a single physical computing node (each one with their characteristics), flexibility to switch between space-shared and time-shared allocation of processing core to virtualized services.

Paper: Modeling and Simulation of Scalable Cloud Computing Environments and the CloudSim toolkit: Challenges and Opportunities

CloudSim is a adiscrete-event cloud simulator which is mostly suitable for simulating IaaS clouds  and cloud data centers. The good think about CloudSim is  that you can easily extend primary classes to create your own modelling and simulation of the desired cloud environments. There are couple of different extensions for  cloudSim for example cloudSim with Power usage modelling and CloudSim with Network modelling in a datacpneter.