Turbo may be on it's way out (will sound odd - but they are quite loud from factory)
Transmission should be very smooth. There will be a little lag when changing gears which is normal. Check that the tiptronic works properly.
the trans should NOT grind at all, if it does it may have been serviced with incorrect fluid.
Rear Anchor Points can leak if not done properly during compliance (water damage is bad, mmmkay?)
There may be an oil leak from the passenger side rocker cover, check for oil stains on the heatshielding and the turbo (both directly below).
If there is, get the yard to change the rocker cover gasket (~$20 part from Nissan, but the intake manifold needs to come off)