I was on EE 2.1 until 2.2 came out and upgraded to 2.2 pretty much immediately.
It all went fine but I’ve noticed that in a brand new install of EE 2.2.1 the setting for “Control Panel index page” is http://domain.com/system/index.php in the upgraded version but http://domain.com/admin.php in the fresh install.
Why the difference? Does it matter?