They definitely have a preference for swallowing across the board. The taste is hard to get past at first, but depending on what he eats and his health, it will taste differently. Semen is mostly glucose and protein, so it is perfectly safe for consumption, in fact, a study a few years ago (I don't remember who conducted it, but you could google it if you wanted) suggested that it had antidepressant properties - so you may end up happier. ^_^
That is a personal choice. If you can do it and don't mind doing it, I say go for it. Some people such as myself, have a gag reflects that prevents them from doing it.
I've never known a guy who doesn't prefer his partner to swallow. Semen is considered nutritious (I believe) as it's loaded with sugars for the sperm to absorb and make their arduous swim. However, as teko suggested, there are many STD's that can be transmitted by oral sex (whether you swallow or not, since germs can be caught in the wrinkly skin). I would recommend only doing it with a serious partner with who you are exclusive and can trust - there's just too many diseases out there to take that chance.
Yes, they tend to like swallowing but it tastes so AWFUL it's hard to do. I choke it down on occasion just to please him.
Yes they prefer you swallow just as we do I mean can you imagine how you would feel if your man had a trash can right there so he could spit every 30 seconds or so as he was going down on you? How would you feel? Do you really think we taste soo much better than they do lol. Just swallow quickly & have something to drink right there to wash it down to get rid of the taste, you can even use the excuse that you got rid of the taste because you didn't think he would want to taste himself & you want to kiss him :)
Monster energy drink. If he drinks it all day, the taste isnt that bad, and if you drink it right afterwards, you wont know you swallowed. My ex drank this religiously. he went to the hospital one day after drinking 8 in a 4 hr period, so i dont reccomend that. but if he drinks it earlier in the day before you go down on him it should taste a little better, atleast it always did on my ex... He always had a can with him, thats how i found out it got rid of the taste after swallowing. So after i would go down, id get a drink, he was okay with that =)