Great company but happiness depends on what project you're on
Pros
Flexible, comfortable, casual work environment. People are friendly, and the Carlsbad campus is very nice. If you're on the right project and are a meaningful contributor, you'll be recognized and typically be given interesting and challenging work. Lots of smart people to learn from. Most employees are very happy. If you're self-motivated, intelligent, and friendly, you'll probably do well at ViaSat.
Cons
Some projects are understaffed and weekends can be necessary to get the work done on time. Schedules can be unreasonable as projects are often won by promising unrealistic short schedules to the customer. If you're not a self-starter, you may get lost in the noise. If you're on a project with a couple of "rock star" engineers, you may not get the interesting work.