Avantages
You will be able to explore every possible technology to work on your projects, there will be no manager to check what you are doing anyway. Very friendly environment, a lot of enthusiast young people. Their tech stack is "everything" literally everything - multiple caching system coexisting together on multiple frameworks with a collection of all the languages out there. A bit of java, PHP, coffescript, backbone, less CSS, ruby, python, go, node, erlang, rabbitmq, scala, clojure, etc... all in one little project. Try to imagine the big ones.
Inconvénients
Unclear responsibility. Pretty much: if it's wrong its your fault, if it's good it's the team achievement. More politics than technology. Refresh your oratory skills if you want to work there, rather than your tech ones. You will be told that everything is wonderful, but expect to be made redundant at any stage, as what is really going on will be carefully hidden. This company went to different phases of "restructuring" and redundancy already. Management is laughable, but you have to obey working on useless projects that might never see any real application a part from keeping you busy until you will be handed a redundancy notice. If you want to work there, make sure you are working on something vital for the company and try to be friendly with the big bosses. - Sad but true.