I've played almost only female characters since 1985. I've gamed with people who play only their own sex, only the other, flip a coin, don't write anything down until expressly asked, make it up to suit the individual character, and so on.
Never had anyone express an issue over it other than the very first time I did it, where the DM of the day for an Arduin game first made me roll bust, hips, waist from a table in the Arduin Grimoire (with no matching columns for the male characters I might add) and then used the game session to have his male 'DM-PC' try to rape my character, and on facing resistance suddenly manifest a black vorpal blade with stars in it and cut my character in two with a single slash that went from crotch up...
(So if anyone ever wonders why I have an irrational bias against Arduin, DM-PCs, and Elric... there's your answer).
In online games I play female toons as well, and the only problem I ever get is people constantly asking 'if the player behind the toon is a girl or not?'
- When they find out, they then insist on referring to my character by references to me rather than her... and have to get beat over the head (not literally, but figuratively) to be reminded to stay In-character... or at least refer to the characters in the game by their names and with the pronouns that fit them rather than the players...
- I get that last problem at the table top a lot too...
I usually combat it by never using a player's name or gender pronoun once the session begins, but only character name and character gender pronoun.
On the online front, for over a year now I've been the owner of a Horde-side adult age guild in World of Warcraft. For the first 4 months there were only 2 or 3 real life males in the entire guild. Toons were of all horde races and sexes, but nobody ever bothered anyone over their 'real life' sex other than the female toons...