Do your research on here and at the open day. If you ask the embarrassing questions they will just shrug their shoulders. It doesn't matter as long as you know what you're getting into which is anything but rosy.
If you're really going to quadruple your salary and if you don't care about seniority in your own country or in living in a soul-less dump then you should definitely take the job. Get your upgrade, get a couple of thousand hours in the left seat then move on. Just don't start complaining in three or four years that things are "suddenly" getting worse.
Good luck.