Pros
As a first working experience it could be a good starting point, but maybe not even in that case you would feel very happy about it. The health care support is good, but it's the only good thing you can receive there.
Cons
So many cons that shouldn't be in a company you would like to work for: - they lied about salaries and cost of life in the area (not just to me: many colleagues fell into the same situation), making you accept a very low salary - they will force the renewal of trial period, making you "smell" the dismissal if you don't accept - no support from the management (in 1y I've been working for them I've seen my manager just twice and one was the same day I signed the contract and I've been introduced to the client) - they try to restrict in any way possible the days of vacation and RTT, forcing you to loose at least 5 days per year - no appraisal for your work: within the client, I've been appraised till gaining a better role than I entered, while Alten refused to rise the salary, nor giving benefits. If you join Alten, do it because you have no alternatives, and start looking for another position as soon as possible.