Hobbyists this weekend successfully posted a downloadable, stock version of the RTM (release to manufacturing) build of Windows Phone 7 Mango. The 7720 build is the reference version and isn't optimized specifically for any one device. As such, some special features may be missing, XDA-Developers forum member itje said.
The OS will work on a core level on most if not all WP7 hardware. Microsoft's chassis guidelines so far have led every phone to run the same Snapdragon processor families and otherwise have much of the same part mix inside.
Upgrading is nonetheless a risky move for most owners since it won't come with Microsoft approval and by definition breaks the warranty. As such, owners who want to patch to a later version of Mango likely won't have an option outside of either getting a separate version of the generic updated build or else reverting back to the original firmware to get back on the usual upgrade path. Microsoft has helped unofficial patchers move back to the official releases but isn't guaranteed to do the same again.
