Here's a version where I used low level surface modeling tecniques like I mentioned before, I worked on one half of the bottle then mirrored it.
I basically seperated the model, lofted edge to edge and applied fillets, this included a bit of trimming here and there.

I did try the method d3 had posted but the area circled in the picture loses tangency to the ajoining surfaces and there were a few naked edges avoiding the bottle to become a solid.