as someone who both entertains, and thinks you should try things i have to ask.
would you rather a guest refuse something based on the dislike or wretch and gag visible so that it is clear they hate what they are eating? Would you rather them at least try it (even if it is clear they get no pleasure in eating it and clearly do not like it) , or would a visible display of fighting the urge to vomit/looking like a contestant on fear factor be worse than just refusing it?
There are some foods that I will react badly too – heck I have been know to gag on pizza after picking the stuff I do not like off just cuz I know it was there and I think I can still taste it (sometime you can taste things even if you pick it off or eat around and sometimes that is still pretty inappropriate) eating around or picking at is not really a discrete option in many circumstance
If you would rather me try it, and get some feeling of respect for trying it for you, I am willing to eat one bite, cough, gag wretch, have watery eyes, and pretty much not want to eat anything else all night.. I am ok with trying new things if people push me provided they do not care about my reaction, and know my typical like and dislikes and thus know my likely reaction,and maybe allow me to say I told you so. I just always thought that would been seen as an insult to suddenly act that way.
I think you've gotten a good sample of answers to this question, based on the earlier posts in this thread.
For me personally, I follow standard etiquette, as many of the previous posters have outlined: If you *can* eat a few bites without showing disgust, eat a few bites, or at least cut it up and push it around the plate a bit. If you simply cannot eat it, avoid it. Eat the other items, praise them to your hostess, and if questioned, say "Oh, the green beans were so good, I filled up on them and just couldn't finish the chicken." Or whatever.
If it's a dessert, a simple "No, thanks," and if pressed, "Oh, I'm trying to cut down on sugar" or "Oh, the beef was so good, I'm so full!" or "Jenny, you're such a good hostess, I was almost full from the appetizers!"
It is perfectly okay to be "too full" to eat at someone's house and stop for fast food on the way home, as long as your hosts never, ever find out.