Hardware Transactional Memory (HTM) is here. Again. It has finally become a common feature in commodity server hardware platforms, and JVMs are gearing up to support it. But what will we do with HTM? This session will explore the underlying mechanics that power HTM on current platforms, focusing on things developers need to understand when contemplating the use of HTM in new and existing code. We will discuss and demonstrate new speculative and optimistic locking mechanisms enabled by HTM, cover benefits and limitations, and speculate (pun intended) about both the near term and long term future impact of HTM on concurrency choices and everyday programming choices.