The comfort aspect of shoe removal is both a strength and a weakness of the case for shoes off at the door.
It is certainly the case that most people will feel more comfortable for having removed their shoes. A 'no-shoes' home is a place of comfort.
The problem is that the western association of removing shoes with comfort and informality may make people more reluctant to accept the idea of removing shoes on more formal occasions even in the home. People may think that it is somehow inappropriate or impolite to go shoeless at a dinner party.
The problem is that in western culture, we have no concept of removing shoes as an act of reverance. The closest thing in the west would be Roman Catholics going barefoot at shrines like St. Patrick's Mount. To us in the west, it is more respectful to keep shoes on than to take them off.
In contrast, in most oriental cultures there is an assocaition of shoes-off with reverance. Muslims do not remove their shoes in Mosques to be more comfortable (though I believe they usually have lovely carpets); they remove them because the Mosque is sacred. Japanese pupils remove their outdoor footwear on arriving at school, not just in order to keep it cleaner, but because the school is a place of authority that is worthy of their esteem.
I dare say that British people will come to appreciate this association of shoes-off with reverance more and more. School pupils in this country are often taken to visit non-Christian places of worship where their shoes must be removed. Thailand has become a very popular tourist destination for British people and there they experience going barefoot in Buddhist temples. More and more they will learn to show respect and reverance to the homes of their friends by taking off their shoes.