At my current project, we've started to initiate a workload estimation based on Use Case Metrics. Apparently several methods exists, but we chose the Gustav Karner methodology. I'm quite impressed with how environmental and technical risks are translated into a factor that can be applied on an initial manhour estimation. Shivprasad koirala wrote a great article that clearly explains the fundamentals of this technique, and Roy Clem provided a summary. As soon as we have real-life metrics I'll update this post. Notice that Sparx System's Enterprise Architect provides full support for Use Case Metrics (including the above mentioned factors).
I’ve written many posts about the strengths and weaknesses of Event Sourcing, but I still thought it might be useful to provide you with a list of the most important practical guidelines and heuristics that I think are needed to be successful with Event Sourcing