Pros
Probably good as a career starter.
Cons
If you are ambitious, have good experience to sell or are a long-time resident in the Netherlands, avoid anything 'Flex'. Regardless, absolutelty do not sign for anything other than a convertible contract after 1 year. There are no benefits, no performance bonuses, will not be put on a pension scheme, and they are pretty much tied up to their agreements with the client. Those are not necessarily transparent to the employee, so things can backfire beyond your control. I am not surprised most hires are from abroad, they can be easily lured with vague promises of professional prospects. If you still choose to go 'Flex', make sure you negotiate and put into writing what your conditions down to the detail. Verbal agreements are not worth anything.