The only time metrics have been useful to me in the past is when they are kept private to each team, which is to say that I do think they are useful for measuring yourself, but not for others to measure you. Taken over time, they can eventual give you a really good idea of what you can deliver. Sandbag a bit (ie, undershoot that number), communicate that to ye olde stakeholders, and everybody's happy that you can actually do what you say you'll do without being stressed out (obviously this doesn't work in startups).