It's an excellent opportunity to metaphorically get inside the mind of Watt and see what made him tick, from the meals he had left outside his workshop heating on the stove, to the 8,430 objects he kept there, which helped to inform him about the way the world worked.
The workshop was left after Watt died in 1819, and locked with its contents untouched. It remained largely this way until 1924, when the decision was made to pack up the complete workshop and its contents and take them to the Science Museum for safekeeping.
The exhibition is free, and is very interesting. It's just a shame that the curved glass - which allows visitors to walk inside the workshop - is so reflective and makes it quite hard to look closely at the many fascinating objects.
For more information, see http://www.sciencemuseum.org.uk/visitmuseum/galleries/watts_workshop.aspx