The possibilities offered by Meterpreter when developing post-exploitation modules are practically limitless. See for example the modules Imager.rb and NBDServer.rb developed by R. Wesley McGrew and presented at Defcon 19 under the title "Covert Post-Exploitation Forensics With Metasploit".
Such modules allow you to make a copy of physical volumes and logical drives on the compromised computer through the network; or mount the file system of those units on the attacker's computer as if they were another device. Not to mention the possibilities from the forensic standpoint that offer this kind of modules.
Much of this flexibility to carry all kind of tasks from a Meterpreter shell is offered by Railgun. This extension allows us to load Windows libraries in runtime and make use of its functions to have full access to the entire Windows API.
