I am using the Qt Creator 2.0.1 (32 bit) at the moment. I have Cygwin installed on my Windows 7 already. I was inclined to use Cygwin's Git command instead of MSysGit (Just a personal preference at this time). That was relatively easy.
I prefer configuring the PATH variable on an application specific basis instead of system-wide settings. I like to keep the system PATH variable as clean as I can.
With Qt Creator, set the environment variable as shown below:
The Git commands are then available from the Menu - Tools > Git