yes; i would think the headband w/ batteries in back may become uncomfortable. or do they counterbalance the light in front?
and - no, no 'tin foil hat' - do the batteries do anything weird to your head? just doesn't seem like a good idea to me . . .
Ever talk on a cell-phone? Use a two-way portable communication device (UHF, VHF, etc.)? Ever stand in front of a microwave?
Yeah, that'll do weird stuff to your head. Placing some batteries on the rear of your dome won't do anything remotely as odd.
Batteries on the rear of the headlamp are quite nice. It allows for a for an easier to adjust front ouput, as the light fixture isn't bogged down by batteries. Once you adjust the light piece, it will stay there, and will not be ungainly. Plus, you can have a larger capacity pack this way. I had some old Princeton Tec lights with 4xAA in front, those were ungainly. Now I have a Princeton Tec Yukon HL with a remote pack of 3xAA. It's quite nice.