-There are adversarial relationships between A and E, between the various offices, and between the various engineering disciplines. There is politics in every company, but since engineers and architects are compared directly, your career promotions, especially as an engineer, can be stalled depending on factors out of your control.
-There is favoritism and disproportionate advocacy for certain individuals.
-Your appraisal is less dependent on the actual quality of your work and skills and much more dependent on how you can appear to be a trailblazer to certain individuals. This can be especially frustrating in engineering, because your skill set needs to be understandable to architects. Due to this you will see people resorting to ridiculous things to gain visibility in the firm.
-There are some great projects to work on, but the average project is not very interesting. The interesting projects are generally reserved for certain individuals.
-HGA does not adequately value technical expertise. If you are not a design architect, there is a low ceiling for your promotion opportunities. HGA will claim to value BIM, project architects, and technical engineers, but that is not recognized in their compensation or promotions tendencies.
HGA will be exciting for a period, but unless you're one of the favored, you can only sit around and be happy for them for so long before deciding to find a new firm that appreciates and values (monetarily) your skillset. Kind of a typical case of a well-intentioned firm that doesn't have enough space to recognize all the talent it has. Maybe a good problem, but they'll lose a lot of good people along the way.