PMP certified PM here - I think the main role of a PM at any company, but particularly a software company, is as a story teller. By that I mean that you are responsible to take the team's status, and put it in terms the stakeholders understand (on the one hand) while taking the stakeholders' goals and putting them in actionable terms for the team to execute (on the other hand). Very few PM tools seem to facilitate this. Many of the corporate ones (as mentioned here and elsewhere) focus on completion in terms of tasks and dollars, and maybe resource assignment and forecast. That's because what folks REALLY want to know - how close am I to getting what I thought I was paying for - is hard to measure objectively. Both because the definition of "what you thought you were getting" is usually squishy, and how close is "good enough" is usually difficult to measure except in terms of whether there is money to make it better or not.
Waterfall tries to address this by making the "what you thought" as rigid as possible, but not surprisingly I can give you exactly what you asked for and you will find it lacking. Agile says I'll give you "good enough" often enough for you to decide when you're done as early as possible, but tends to be difficult to time box. My .02 worth anyway...