From: Near Portland, OR
After I learned russian, I went on a language learning spree. Mandarin, Japanese, Arabic, Mongolian, Korean and Navajo.
I never mastered any of them on a conversational level, but I did learn that Korean and Navajo were by far the hardest to master. And of these two, Navajo is just insanely hard. So many tones..
I've lost track of her now, but I had a friend from an internet group from Israel. I met her when she came to the US. Her natural linguistic talent was amazing. She had been born in the Crimea and emigrated to Israel when she was a child. She learned English from watching TV, it was her third language and she could speak perfect English with either a middle class London or New York accent.
She had been to London a number of times and she said she always used the American accent there because the British tended to treat her better if they thought she was an American tourist. One time she met a cousin there who had grown up in the UK and had a British accent and her cousin commented on her American accent when they met up. She said it did feel awkward so she closed her eyes for a second and switched to her London accent. Her cousin was blown away.
She was here for a weekend gathering of our internet group and we kept forgetting she wasn't American. The only time we remembered was when someone used some American slang that she didn't know.
She was taking a gap year between her mandatory military enlistment and college. When I lost track of her she was studying Mandarin and I think some other language. She did say Mandarin was toughest language to master she had ever tried to learn.
I am, unfortunately, mono-lingual. I managed to barely get by learning German in high school (most US high schools have a 2 years of a foreign language requirement, or did then). My SO is 1st generation American on her father's side (she doesn't know how long her mother's family have been here, they were basically hill folk and she doesn't have anything to do with them). Her Spanish vocabulary isn't huge because her mother had a problem with her learning other languages, but her accent is perfect. When she does try to speak Spanish the recipient is usually confused because her accent is a perfect middle class Mexican accent, but she stumbles over the words.
I grew up in a multi-ethnic neighborhood with Hispanics, Japanese, Koreans, and Chinese and never managed to pick up much of any of those languages even though I had friends who spoke other languages at home.
I am pretty decent with British slang and I liked messing with my immigrant British friend and his sister by using British slang with my American accent. It did their head in.
People who can be completely fluent in multiple languages impresses me no end.
WitP AE - Test team lead, programmer