OK, so you get into this device, it transforms your atoms to energy of some kind and rebuilds it again at some other location.
The question is: is it really you or just a copy of you?
Define the "real you."
For arguments sake let's do away with the idea that we have an internal spirit or "soul" for a moment.
When transported, are you still "that" person or did you just happened to die and blink out of existence to be replaced by a perfect copy, atom by atom, of you with the universe no wiser to the fact that the "original" you is long gone?
If this technology ever does come to pass, it will pose some difficult questions such as this.