In earlier work, we were the first to investigate the potential of using graphics processing units (GPUs) to speed up explicit-state model checking. Back then, the conclusion was clearly that this potential exists, having measured speed-ups of around 10 times, compared to state of- the-art single-core model checking. In this paper, we present a new version of our GPU model checker, GPUexplore. Since publication of our earlier work, we have identified and implemented several approaches to improve the performance of the model checker considerably. These include enhanced lock-less hashing of the states and improved thread synchronizations. We discuss experimental results that show the impact of both the progress in hardware in the last few years and our proposed optimisations. The new version of GPUexplore running on state-of the- art hardware can be more than 100 times faster than a sequential implementation for large models and is on average eight times faster than the previous version of the tool running on the same hardware.