Well, Amazon was at least half right. As the retailer predicted, Microsoft did make Windows Vista Service Pack 1 available for download on Tuesday via Windows Update and on its Web site.
Still unclear is when it will start being available on retail shelves. Amazon said it will start shipping boxed copies with SP1 included on Wednesday, while Microsoft said it will be at retailers "as soon as April." I've asked for further clarification on the disparity, but have yet to hear back.