Is this something new? And what is the advantage of using this instead of the conventional paper and pencil they use to give?

No advantage. It will make things harder and waste your time while ereasing.
Make sure you keep your dry marker caped when not using it. Those cheap ones dry very quick.
I think they started sometime beginning of this year.

Are you forced to use this sheet or can you ask for a pencil and paper?

All DAT must use laminated sheet. You have no choice.

I took the DAT feb 2007 and am gonna retake it soon i got 19 AA and 17 PA is the test very different from the feb test because i have been reading that QR became ridiculous, and is the laminated sheet white or clear?

Each test center might have different color but I think I had yellow. For sure, it wasn't white. I took my first one during Apr of 07. I was never informed that I will be getting laminated sheet. I really struggled on QR with those thick dry markers.

my laminated sheet was pink with really strange lines on it....it looked like a grid...

Get a dry erase board to practice with. Cheap and you get the same effect.