All you guys have jumped the gun. You should have more faith in the developer community. the folks over at Liliputing have just publishing how to continue sideloading 3rd party downloads even if you have the new 1.4.1 upgrade installed and a rooted NT is NOT a requirement.
Here......Merry Christmas.......now get to work.
http://liliputing.com/2011/12/sidelo...-required.html