As a male:
If they are pre-op female to male, then it doesnt matter to me because theyre going to be in a cubicle not standing at the urinal next to me. Unless theyve really, really been practicing.
If they are post-op, then Im not going to know because I dont have "dna vision". At best I could say that they look kind of feminine, which isnt the same thing.
Im not particularly into standing around with people in the toilets at the best of times. I dont see any reason to feel differently if theyre genetically male, genetically female, or transgender. Location would make a different in only one instance - my own bathroom - in which case Id ask them "Who are you and why are you in my bathroom?!"