Well, I guess I can be the first person to report finding the GH Cantina packs (at least in this particular forum). The local Wal-Mart (in VA) had two of each set on the shelf this morning under a slightly modified SW action figure section. I came very close to picking up the one with the Modal Nodes (just for the music), but I passed on them. No sign of the exclusive comic packs, although WM stocked the pegs full of the "new" Han ST/Chewie, GMT/Stormie, Luke ST/R2-D2 wave without the blue markings.
So, for whatever it's worth given how horrible Wal-Mart's exclusive distribution is, the GH sets are out there.