The reason I say stick with conventional oil, is that Subaru specs a conventional oil for break-in from the factory and as I recall, does not recommend a first change for 7500 miles. If they are supplying it with conventional, and the car does require a break in, I would not change to synthetic until the break-in period is over. I would change to synthetic before "getting on it for real."
I'm not saying that synthetic(especially a group III) would cause problems, but when in doubt, go with the manufacturers example.
I remember someone saying how for the first X miles, you were basically not supposed to use the turbo
Whenever the manual say's it is OK to drive normally, that is when I would switch to synthetic. I'd probably go with Mobil 1 0W40 or if warranty constrains to 10W30, Schaeffers.