Brillouin distributed optical fibre sensing has been a subject of intense research and industrial development for more than twenty years, demonstrating its capabilities to be an effective and powerful measurement tool for a wide range of applications. Making use of sophisticated implementations, remarkable progresses on the sensing performance have been reported in the last decade, allowing significant improvements in spatial resolution and sensing range. However, the demand for distributed sensors with more performing features is steadily growing, imposing new and more challenging requirements to the sensor design. This paper presents a brief overview of the fundamentals of Brillouin distributed fibre sensing and reviews the main current limitations and challenges faced when the sensing capabilities are pushed beyond the state-of-the-art. Different possible approaches and methods to enhance and compare the sensing performance are also discussed.