Pros
Criteo has the financial health to make material life easy. The building is nice, with fancy decoration. You can have the tools you need if you ask for them (eg: all-inclusive JetBrains subscription).
Cons
Criteo's R&D is growing, there are more and more people (near 600 at the time I write this review). That makes team's topics more and more specific: it is a good way to become an expert but can become boring when you expect to discover many different things. Management needs to improve. It is mainly engineers that got "promoted" without any management or leadership background. The trainings are quite poor (a few days without follow up). It leads to some violent management situations, sometimes with moral harassment. Information is very often on a "need to know" basis. If you know the right people (and if they like you), you have the information. If not, you may miss it (and it may impact your work). Issues tend to be worked on with money. Talking could sometimes be more efficient.