Pluspunten
I worked in the Visual Search team in A9 for two years before joining another company about 6 months ago. So I can only comment about the visual search team. A9 offers a good compensation package which is at par with all the other good Bay Area companies.
Minpunten
Everything else except pay pretty much sucks here. Regarding the facilities, they have just two buildings rented in Palo Alto and no campus what so ever. The buildings are over crowded and even the coffee and snacks suck. They provide no gym facilities either. Regarding the team, Visual search team was formed from a start up which Amazon acquired some time back. Couple of guys from the original start up control everything. These two guys are very arrogant, dominating and take up all the good projects. A9 recently hired a lot of super smart engineers with Ph.D., but they are forced to do crappy development work by these guys and eventually move out to better places.