I know of at least 3 times that I've eaten horse meat, and I have no issues or complaints. On 2 occasions it was a surprise, and once I ordered it knowingly. In all cases, it has been outside of the U.S.
The first time was 6 years ago at a large party a friend of mine hosted at his house near Barcelona, Spain. Basically, it was a barbecue with several different types of meats cooked on a giant grill then passed around on large platters. They also had large platters of cured meats, primarily pork (hams, sausages, etc.). When I asked the host what cuts of the grilled meats were he responded by saying "carne de res, carne de cerdo, and carne de caballo". In translation, I was good with the first two, beef and pork, but was a little stumped on the third meat. After a couple minutes, it hit me - horse. It was actually quite good even though I later found out that it was a pony.
I had a very similar experience at a party held at a winery in Mendoza, Argentina earlier this year. However, no cerdo - just res and caballo. My host told me that Argentina was the world's largest exporter of horse meat for human consumption with most of it going to France and Belgium.
My favorite and most memorable horse meat experience happened about 3 years ago on a business trip to Verona, Italy when my wife decided to join me. Our first day there, we spent the afternoon there strolling around with my wife doing the Romeo and Juliet thing. Evening approached and we decided to get something to eat, preferably simple as we had been snacking earlier at a few wine bars. Appropriately, I chose a restaurant known as Osteria Giulietta e Romeo.
After looking at the menu I decided to order Pastissada de Caval, which I knew was horse meat stew, though I didn't translate it for my wife. My wife was having trouble with the menu, but said she wanted some type of pasta. A minute later, our waiter passed by with a dish of thick spaghetti with a rich looking meat sauce, and my wife said "that looks good". When the waiter, who spoke no English, returned, I asked him in my limited Italian, what the dish was and he said "Bigoli con Ragu d' Asino. I told my wife that it was simply pasta in a meat sauce and she ordered it.
The meals were served, and we each enjoyed them very much. My wife tried the stew and said while she liked it, she liked her pasta and sauce even better. I sampled her dish and found the sauce to really be outstanding. When the waiter returned, I pointed to the sauce and said "Che tipo de carne?" (What kind of meat?). He replied by saying "Asino". I told him that I didn't understand and he replied with "Col musso". I shrugged my shoulders and he discreetly leaned over the table and went "Hee Haw, Hee Haw". I then informed my wife that the sauce she loved was made with donkey meat aka mule aka ass.
She hasn't forgiven me yet.