Israelis take you much more serious when you speak Hebrew to them. Most of them speak English, and most pretty fluently, but when you speak in Hebrew to them, they not only understand you better, they take you more seriously. At a restaurant when ordering food, on the bus asking for directions, at a store looking to buy something---the difference between English and Hebrew is surprising.
There's a whole sort of stigma and stereotype when it comes to speaking English. Sometimes I have to be really pushy and say, "I don't speak English, talk to me in Hebrew" to maybe get a cheaper deal at a store, or for an Israeli to feel more comfortable telling me what/how to do something.
For example, on Friday I took the bus down from Haifa to a town a little north of Tel Aviv called Ra'anana, famous in Israel for being home to many Americans. I got on the bus, and the bus driver asked me where I wanted to go (in Hebrew). I told him that I wanted to go to Ra'anana (with an American accent) and he told me that it was 25 sheckles, in English. Now that he knew I was American, he spoke to me on a whole different level. He didn't cheat me, and it wasn't anymore expensive than it normally was, but because he knew that I was American, I felt like our conversation was on a different level.
And I find that it's very hard to talk to Israelis my age. They speak so quickly and with so much slang that it's often very hard to understand them, plus they all speak English pretty well. But, I volunteer at a Holocaust survivors center, and I find that it's very easy to speak to the elderly because they don't know English and they speak very slowly. It's also easy to speak to my Hebrew professor, of course.
I've been working on trying to speak Hebrew with more of an Israeli accent, but it's really hard. I'm starting to think that speaking Hebrew with more of an Israeli accent is more important than knowing vocab. I have two more months here, so we'll see.