Oh sure, most people in the ROM cookign community know about this little story as there have been many,many variations with some form of WM 6.1 for a few months now. But it's a slow news day, so why not?
Word is this ROM (3.49, radio 3.39.10) for Sprint is indeed the "almost official, but still technically beta" WM 6.1 update that many are expecting this summer from Sprint.
Source: WM Experts
