I filed mine on April 25 and still waiting. USCIS announced that all receipt notice for petitions in April are delayed by two week.Normally it takes about 2 weeks to receive notice. But due to delay, it may take about 1 month. I am expecting mine in coming two weeks but have to be patient. But be positive and be flexible. Check the delay here:
http://www.usvisanews.com/articles/memo2469.shtml