From my limited JK experience it's not normal. This is my 6th Jeep, first JK - no vibration or anything other than perfectly smooth. I agree with the second opinion. Either that or ride it out for another couple of thousand miles and have them replace it under warranty.
Colorado Mountains = Land of Mountain Trails
And now these three remain: faith, hope and love. But the greatest of these is love. 1 Corinthians 13
'08 JK Sahara, Jeep Green, BFG MT's, Pro Comp 4" Lift, Smittybuilt XRC8 Winch, Olympic BOA front & Olympic Defender rear bumpers, Olympic A/T Slider Rails, Spidertrax Spacers, SeatGlover Seat Covers, Bestop TrekTop, Husky Mats, Midland 75-822 CB, Magellan Maestro 3250.