Pros
Dynavac is a great place to hone your skills. The wide variety and scale of work, materials you work with, and experience there makes for great development potential.
Cons
Management has a tendency to disregard the "real life" situation on the floor. There could be consistent work but, looking back on my employment there, the job bidding and work flow was poorly managed. Benefits were par for the course. Nothing that really made them stand out but packages are available. Much of the time lost on jobs could be prevented by having more observant and seasoned engineers. My biggest complaint is that feedback was not well received. In areas where mistakes were clearly made and could be prevented in the future, feedback pertaining to these mistakes (which was always very constructive in nature) was seen as insubordinate.