Mine doesnt want to start when it sits in the cold. Sounds very similar to what you're experiencing. I thought I would be stranded at my gf's house on Thanksgiving. At first it wouldnt start - it would turn over just not start. So as I was turning the key I'd give it a little gas, revving the engine up until it was running. It took some doing but I got it going. But if I put it into gear, it would just stall out. So I ended up getting it started up again and it sat for 10 minutes in park while it warmed up. Ten minutes went by and everything was fine - went right into gear no problems.

The Subaru dude recommended checking a sensor, so he checked it out when I had the oil changed. The sensor is fine. He speculated cleaning the throttle body would take care of it. So we'll see...