A lot of people have started to see MCell appear next to the ATT logo since the second beta of 3.1. MCell is basically giving you 3G service from a broadband connection, if you or someone has a MCell router. 3.1 is simply now able to tell you if you're running off of regular 3G from a cell tower or from a router that gives off a 3G signal. MCell is useful if you get bad service around your house or office and you want to make 3G service usable.