Pros
HDR has grown by acquiring many small firms that were successful and has thus employed many talented individuals. Working with some of those individuals can be a distinct pleasure. HDR also seems to generally strive to keep this talent from walking out the door. As an example, individuals with specialized capabilities such as wastewater treatment plant design aren't put on the streets once a project ends.
Kontras
Management processes tend to be applied bureaucratically. Individuals who have demonstrated successful track records for many years will still be required to conform to mind-numbing procedures that are basically designed to capture the errors of those who are either less seasoned or talented. The talent that was acquired from smaller successful firms may not thrive in this environment.