As usual I agree with Polarbear. While my dd did not have any social issues there were certainly other areas of concern that I wish we had jumped on earlier. People had difficulty understanding her speech. We were told it was likely because she was using such advanced vocabulary that people didn't expect it from her so they were taken aback and noticed that instead of listening to what she was saying. This combined with using words her mouth wasn't really developmentally ready to say so they came out unclear. Now in first grade she has started working with the speech therapist. By now, though, it has combined with some of her other ld issues so things like sounding out words is harder. She writes words phonetically correctly for how she is pronouncing them but is often pronouncing them all wrong. A bit of speech therapy at 3 or 4 might have reduced her issues now.
As for the not playing along with other kids if she can't be in control - it reminds me of my nephew who recently turned 21. He always was that way and his parents just thought he had "a difficult personality" and were sure that they were smarter than the teachers. I have assumed he is likely somewhere on the autism spectrum but can't understand how it was never caught - maybe his parents just didn't want to hear it when the issue was raised. Anyway, despite being absolutely brilliant he dropped out of high school and was unable to complete class after class at the local community college after receiving a GED. He simply CAN'T get himself to do things the way other's want. It is his way or no way. So now this brilliant young man is living in his father's basement - no school, no job. He has decided to devote himself to creating a web comic for the next 5 years because no one will try to tell him what to do. I saw him over Christmas and he complained several times about how much he wished he could have even 1 friend... So it may be no problem at all as islandofapples says or it could be an indicator of potential problems down the road. Personally I would take the preschool's input very seriously on this one.
JMHO...
