Based on Playbook performance, using QNX was one of best choices they ever made. Before that, OK Labs was already deploying user-mode version of popular operating systems on OKL4 microkernel. It's what Blackberry should've done so they get benefits of both ecosystems + rock-solid core. Actually, they should've tried to outbid General Dynamics for OK Labs to just get their people to do the project using their experience. I'd have bought them instead of QNX probably but looking back I'd consider grabbing both. Then dual-license both stacks for personal use to let the OSS improvements roll in. :)