Pros
I consider myself a Silicon Valley veteran as I've worked for quite a few companies in the valley. Criteo is one of the greatest companies I've worked for.
Lots of smart and talented people. Some of them are super nice too. :)
Top notch pay and benefits (has to be deserved, obviously).
Flat structure. This implies that employees are treated as adults and expected to behave like adults.
Open and honest communication from the top (very little BS or propaganda)
Truly diverse with all ages, origins, accents, genders, and orientations treated with respect. Everybody is encouraged to be themselves and treat each other with respect.
Voyager program designed for those who want to work for a month in other parts of the world. (The travel policy though is not very friendly to those with families and kids.)
After you have earned some karma, you'll have freedom to do what you think is important (which sometimes can run into some political barriers)
It is a midsize company which means that there are enough resources to support you and that you can still have a meaningful impact on company's bottom line
A lot of focus on hiring the right people. I think it is super important.
Lots of challenges and opportunities
Cons
A bit slow to deal with people who don't fit well. (though there is a delicate balance)
"One size fits all" travel policy is too restrictive for employees with families.
ESPP is missing to make the perks package complete
The company is growing so fast that there is a legitimate concern over maintaining the company culture.