It appears that those who managed to flash their handsets with the leaked RTM build of Windows Phone Mango are a-okay to update to Mango. We've had a few reports from readers on different carriers (Verizon and Deutsche Telekom to name a few) that they've successfully updated to the latest version from the RTM build.
Some users on Twitter are also confirming that they are able to update straight to Mango so it looks like everyone should be in the clear to updated safely. While it's not officially supported by the WP team, let us know how you get on in the comments.
Thanks W.R and everyone else for the heads up!