From what I can tell, it seems to be the launcher that won't die, not minecraft.
If you've got both running, you should notice you have two of javaw.exe running in the process tab. After closing the launcher, the associated process doesn't see to die with it.
You can kill the process and minecraft will continue running just fine, and seems to terminate correctly afterward. You might need to be on an administrator account to kill it though.
John Caskey
From what I can tell, it seems to be the launcher that won't die, not minecraft.
If you've got both running, you should notice you have two of javaw.exe running in the process tab. After closing the launcher, the associated process doesn't see to die with it.
You can kill the process and minecraft will continue running just fine, and seems to terminate correctly afterward. You might need to be on an administrator account to kill it though.