I'm in almost the same kind of position, but with more complications.

Until 2 weeks ago, i was an external consultant, moving across to the client employ discretely so as not to advertise that the consulting company was letting this happen.

A few people in the team here know what's happened, but there are few who don't. The new position puts me as a team leader, not a developer, so i've also been promoted from grunt to boss.

The coincidence is that at around the same time, more work came in that required me to take a step back and manage it as a whole, and use my knowledge and expertise to take a supervisor role in projects i wouldnt normally have had anything to do with.

While i can get away with not seeming like the boss until i get permanant (not consultant) bodies in the team who will know what's going on, i will be keeping my eyes on how you deal with your transition and hopefully learn a few tips that will help me in the time to come.

Best of luck!