Yes, I went this week. A rare opportunity in Britain to see Adams' own prints he made at the time, most of which have been lent by institutions in the USA. Its a must if you print your own photos, or love landscape photography. Seeing the quality of the real print was fantastic, and a huge difference to calendar reproductions! There is also some filmed extracts of Adams talking about his work too.
And while you're in London, the Klein/Moriyama exhibition at the Tate Modern is un-missable too.