All NWS offices in the Southeast and Mid-Atlantic are doing 6-hour upper air launches, and the hurricane hunters are dropping numerous dropsondes in and ahead of Irene. Everything commenced yesterday afternoon and will continue until NHC orders us to stop. All of this extra data is being fed into the models, so I'm not surprised how much change you've all observed in Irene's track over the past 24 hours.
I think the Outer Banks and New England have the highest risk of landfall now. Florida, Georgia, and South Carolina will probably get a close brush as it parallels the coast.