Will be interesting to see. The droid did great in the signal department and it was all metal, though Motorola does a much better job with radios than Samsung. Would be unfortunate for Samsung if they tout a higher end experience in the alpha and the radios are crappy.
In my situation the regular S5 gave me the same signal in my dead zone house as my Maxx when I tested it at launch. Samsung has made some good improvements in radio, but I still don't think they'll get to where Motorola is. Their focus lies on screen and camera.