There's no official WM 6.1 update for the Tilt (yet). There is one for HTC TyTN II. There are also custom ROMs that are WM 6.1 based available. You can find them at xda: (http://forum.xda-developers.com/forumdisplay.php?f=378). (Try the custom ROMs at your own risk. Read the FAQs if you never tried a custom ROM.)