It works well in Chapter 2 and isn't bad for Chapter 3, packing a nice punch with its attack. It follows you all the time and it may divert enemies into running toward it rather than you.
Unfortunately, Dogmeat may run right into explosives, killing itself in a fate similar to the original Dogmeat in the Mariposa Military Base in Fallout. However, It will respawn when you reach the next save point.
Dogmeat is a reference to Mad Max 2 (aka The Road Warrior) and A Boy and His Dog. Both movies featured a lone wanderer and his dog-companion in a post-apocalyptic world, and in the latter movie, the main character uses "Dogmeat" as a disparaging nickname for his companion.