I've had two girlfriends, both of whom shared serious relationships with me. Both took the idea of enjoying tickling in stride because it's fairly normal play-ish behaviour. They listened to me explain my attraction to feet in detail as well, and while we really cared about each other in both cases, I think that neither was completely comfortable with it because they didn't understand exactly what it was like to have that fetish. Their concerns included that I might be seduced by another person because of that weakness, and that if I were to glean sexual pleasure from their feet, that I was merely objectifying and not really caring about "her." While I can imagine that someone might develop these concerns for a lack of understanding of what it's like to have a fetish like this one, neither was warranted (nor does either describe a circumstance that I had ever even considered).
The toughest thing about being in my position is that with two experiences with such parallel resemblance, it's almost automatic to think that "all women" would have the same feelings given the same truthful description of me. Logically, though, I've never found it easy to believe that women and men are all that different, and it seems almost impossible to think that zero members of the opposite sex would enjoy the knowledge of a vulnerability like this in a guy they knew.