I've always hated using the women's restrooms for as long as I can remember; I've always felt awkward and as though I didn't belong (which I didn't) and it has always earned me weird looks, even during junior high and high school. Consequently, personal history has resulted in a habit of holding it when out and about and in public unless I really, truly could not. This has been true even during school and on road trips.
For a little while now I have been using men's restrooms when in public, though I still retain the habit of preferring to hold for the most part. I have never had a problem doing so, and even when there are other men (or boys) in there it has been as smooth and natural a thing as there could be. Have even exchanged a nod or two.
I've actually refused to use a restroom when pointed to the women's and deciding I didn't want to deal with that (especially as they were visible from just about the entire restaurant): fortunately, I only needed to wash my hands. I made do with napkins instead.
Where I work currently, however, there are no employee restrooms and the only option is men's or women's -- I'm also not out at this job and the smock I have to wear apparently hinders passing (it was actually something I needed to adjust to, the fact that I was pegged so often and so easily as female). It feels wrong using the women's restroom even there, even with a uniform, and I dread needing to use the bathroom. Often I have no choice though. I end up feeling like I'm doing something illegal with the precautions I take. It's seriously ridiculous. Not to mention anymore I get paranoid that a mother will either think I'm in the wrong restroom or determine me to be an unknown and jump to the conclusion that I'm a pedo (because I know there's mothers out there like that) -- does anyone else deal with that concern? Or am I just strange?
As for the claim that men's rooms are dirty and gross: I personally haven't seen that to be anything more than a stereotype. I've worked in retail for some time now and so have heard stories about the bathrooms, I've also had to clean them on occasion at my last job (which was at a gas station convenience store at that), and there's really little difference (at least in my area and experience). Believe me: women's restrooms can be horrendous while the men's has been virtually spotless or just a little dirty. As for the mention of men not feeling any reason not to ->-bleeped-<- and piss all over, I can guarantee that some women don't either -- with the extra bonus that they also have a time of month if you get what I'm saying. I've never noticed a difference in the restrooms I've only used either...perhaps it depends on the type of establishment and/or whether they clean their restrooms regularly, but I've also had people support my experience from different areas, so take from this what you will.