I had an alignment done a couple weeks (by my independent, not the dealer...), but my car is still moving too much laterally with any bit of wind. I think the wind makes the movement more obvious, but I can notice it a little at anytime.
My new alignment did make the car more stable...it was done to different specs this time. I guess Mercedes put out a service bulletin for alignment to compensate for cross wind, and that's what it's aligned to now. I am a little concerned about my 4 month old tires wearing out unevenly (feathering, perhaps), but since it was a Mercedes bulletin, I guess they won't.
I also had the 30k service done at the same time, and my mechanic looked over the car well for bushing wear and other worn suspension components, but they said it looks fine in those areas. The only thing I know that I need to replace are my motor mounts. Would collapsed motor mounts cause my front end to act "loose" and cause the car to move side-to-side? Would winds tend to blow the motor around just enough to cause the car to act this way? I can't tell if it acts worse on grooved pavement as opposed to a smooth road, but sometimes it seems to. I wonder if it could be some other suspension component?