The blog "Reification of Persons and Personification of Things" gives a nice endorsement of the Heinrich Capital Introduction (at the end of a critique of David Harvey's):
"As a result, Harvey’s stated attempt to provide a close reading that reads Capital in ‘Marx’s own terms’ ultimately fails. Fortunately, the recently published Heinrich introduction does address these issues. It is also properly lucid and cogent providing an overview of all three volumes of Capital in half of the space it takes Harvey to give an overview of volume 1. If I had my say it would become the go to guide not only for people who are trying to understand Capital, but for a number of people who think they already understand Capital."