RIM's co-CEOs shot back at mixed early BlackBerry PlayBook reviews that savaged the tablet for the unfinished state of its software. The company's Jim Balsille didn't believe it was "fair" that people attacked the PlayBook for the lack of native e-mail, calendaring and other core apps. The device was perfectly usable by the roughly 60 million existing BlackBerry owners, he told Bloomberg, as they could bridge their phone to the PlayBook and check the information stored on the BlackBerry itself.