I wonder what shoes I'm actually wearing, probably look down to find out. Then I'd say thanks and wonder why he noticed since guys don't usually pay attention to shoes. Depending on a lot of other stuff, I might think he was flirting or I might just think he actually liked my shoes...If he compliments me on my earrings, same kind of deal...If you're actively trying to flirt- it's just best to say "you look nice/pretty today"- that one is pretty clear and I'm flattered even if you're not flirting.
I'd wonder how he noticed them because guys are oblivious to most details. And it would also depend on what tone he said it in to me. But I would either think he is gay, or is really trying hard to get my attention without sounding too obvious. That's my take on it!
Girls are hard to grasp sometimes. We can't say nice boobs or nice face. Picking apart analytically the facial features and body shapes even for a compliment's sake is freaky. Eyes - cliche.
I think it depends on the situation. I don't think we can trust the girls' specific responses here because absent of context, they jump to conclusions.
If the shoes are nice and so are the feet in them (no cankles or toes visibly tortured/deformed from too-small footwear, or bad pedicure), I think most girls don't mind one bit of they receive some recognition. Many girls are mad crazy about their shoes and spend way too much money on them and are very proud of them.