For team members working in an agile software development environment (if you are not already, it is simply a matter of time), the principles of the old Project Management Triangle still apply. How the cost, scope, and schedule are balanced will always determine the quality (i.e. success) of the project, and this needs to be assessed with each project (i.e. the client requirements). Unfortunately, no one is immune to senior management and project managers trying to upset the balance of the PM Triangle by reducing costs, tightening deadlines, and adding features in the specification (most likely to try and make a sale).
UX and Agile: Tying the knot by Michael Lai