I've dated girls before. Obviously, performance will improve because the sex will always improve with someone that is willing to make you satisfied. Also, the longer you have sex with someone the more you will both learn each other's preferences and rhythms.
It depends on the girl just like in any dating situation. There are crazy girls and good ones. The main difference you'll learn is that their standard of living is different because they make significantly more than you. Even if you're a wealthy professional, don't think you make more than her. Don't try to keep up with her spending or her income. If you get into a financial dick measuring contest, then you're going to get wrecked and humiliated.
Her friends are mostly in the industry, so they're usually open to sex related topics and dirty jokes. But, I've found that a lot of their friends are open to having a lot of sex with you as well. When girls know you as a man that is not a "client," their willingness to have casual sex with you increases dramatically.
You're probably going to enjoy your time together and the main source of contention is her work. Most men can't accept their work in the long-run due to catching feelings. Also, the fact that it is socially unacceptable is something that will affect both of you, whether you realize it or not.
There are risks to both sides. The reason why most girls are weary of dating is because a lot of the guys that they end up dating are using them. This may be for financial gain, sex or other things. Its sad but most guys are just in it for their own gain.
On the other end, there are many women that are just playing the long game and are probably just milking you too.
It's a complicated situation. I suggest anyone going into it just be honest with yourself and the girl. Don't be an asshole and don't get fooled either. Enjoy the present and you'll save yourself a good deal of problems.