Until recently, I couldn't communicate with Siri because my accent. Thanks to my accent reduction training, now Siri understands me very well. It's like I got a new girlfriend with beautiful voice. By the way, I set Siri with a female voice with American accent.
To understand Siri is another story. At the beginning, I had a hard time to understand her sentences. It's her intonation that makes me confused sometimes. I'm getting used to it these days though. Listening is much harder than speaking because you don't have any control over listening. You just need to listen and comprehend.
Language acquisition boils down to immersion and Siri helps me a lot! Thank you Siri!