Hayden James from Pinstack.com has figured out a way to install BlackBerry OS 4.1 on 71xx series and 72xx series BlackBerry devices. This installation is only about 7 steps and takes roughly 20 minutes but understand that this procedure is not supported by Pinstack.com.
You can find the Install instructions here…
Don’t upgrade your 72XX to 4.1 unless you have an official version from your carrier! All sorts of important functions break! This is a case where having the latest and greatest, is not in fact the greatest. I tried it and I say skip it.