I have a bottle of Blanton's with a fairly noticeable vertical gap starting at the top of the cork and going 75% of the way down to the bottom, and I highly doubt the integrity of this for long term storage. I just today had the cork on a bottle of Peter Jake's Private Keep start to break. All of the corks on my various scotches are dry, as they have been sitting during the summer while my bourbons, ryes, and canadians get my focus.
Now personally, I could care less if the bottle has a screw top, or a synthetic stopper. I just don't feel that cork is a really good material. It dries out, becomes brittle, and can taint the whiskey. I would love to see corks start to disappear, but I don't see it happening as corks are more eloquent.
Pendleton has a good compromise by making the stopper out of rubber. It provides a good seal, it doesn't have that cheapness that a screw top gives, and it will hold up over time.

