I agree, QNX paired with the hardware of the Playbook was better than any iPad or Android tablet even up to this day. Unfortunately that meant nothing because of the lack of apps.
That is why I think Blackberry has a shot at a come back because I assume (I haven't tried one yet) that BB10 is a significant improvement over the QNX in the Playbook. And that device already had the best multitasking I've seen and it had solid battery life as well. My Playbook gets better battery life than my six month old Nexus 7.