I think I qualify to answer!
I have a number of issues but not to do with anatomy! I don't wear special underwear
If I ever book a ride and go with a female they almost always automatically assume that I can't ride, whatever I say. Apparently its very common for ladies to bring their boyfriends/husband who can't ride, but get them to claim that they can. This means that the first time I go I end up with the steady Eddy mount (and I'm definitely not a steady Eddy sort of person!)
Its also a problem to get riding clothing. Want a pair of long boots? Biggest size for most brands is 8. A pair of Mark Todd waterproof riding trousers? - only for ladies (I presume Mark Todd wears the ladies version?). A pair of cheap jods/breeches? forget it! (remember the thread about the Aldi equine stuff)
Never mind - I'll have a read of my horse magazine - they have a nice group test of show jackets. Oh - they have only tested ladies jackets
I'll enter the competition to win jods/boots etc - nope - only for ladies.
These points aside I actually find it rather fun spending my time with a crowd of horsey females!