Regrettable. Career ruining.The good thingsIt’s a job, which is better than no job while you look for another job. May eventually lead to a permanent role with client company.
The challengesYou’re not really working for them, but for the client and you’re not a part of that company, so they can pretty much do what they want and your employer has to bow to them as that’s who counts, not you. You are expendable.