A couple years ago when I started playing with vagrant to setup both windows and linux VMs, I wished there was a powershell equivalent of Vagrant's ssh command that would drop me into a powershell session on the windows vagrant box. Sure its simple enough to find the IP and winrm port of the box and run Enter-PSSession with the credentials given to vagrant, but a simple "vagrant powershell" just makes it so much more seamless.
After gaining some familiarity with ruby, I submitted a PR to the vagrant github repo implementing this command. The command essentially shells out to powershell.exe and runs Enter-PSSession pointing to the vagrant guest using the same credentials that the vagrant's winrm communicator uses. Additionally, it temporarily adds the vagrant winrm endpoint to the host's Trusted Host entries, restoring the original entries once the command exits.
Its been a good while since that submission, but I'm excited to see it released in this week's first minor version update since that time.
Small bug/annoyance
Note that the up and down arrow keys do not cycle through command history. While I thought that was working a ways back, its possible that other changes around vagrant's handling of subprocesses caused this to pop up. At any rate, I just submitted a fix for that today and hope it is merged by the next bug fix release.
Only works on windows
The vagrant powershell command is only available on Windows hosts. Currently there is no cross platform implementation of the Powershell Remoting Protocol. There is a ruby based winrm repl but it is extremely limited compared to a true powershell session. However, the vagrant powershell command does provide a --command argument for running ad hoc non-interactive commands on the vagrant box. It would be easy to at least support that on non windows boxes.