When Slacker launched its big software overhaul in February, many were skeptical that a refresh could bring it back to prominence. Apparently, all that doubt was misguided: Slacker says it's racked up 6 million new listeners in the past three months, 3.5 million of which are on mobile. They're more involved, too -- there are 100,000 new paying customers, iOS installs have tripled and members of all kinds tune in for an average o
