This device has taught me so much about how my body reacts to alcohol, I am a more informed drinker now. And it's a fun way to keep your friends from driving drunk.
I've had my breathalyzer for about a month now and it seems perfectly accurate. Accuracy is the one thing I was worried about when choosing one, and mine had been perfect. Just always wait the recommended 15 minutes after eating or drinking anything! A friend of mine blew a .16, then had a sip of beer, and blew a .45! The remaining alcohol in your mouth will completely skew the results. Just follow the directions, wait 15 minutes, and it'll work perfectly.
I bought mine online back in Feb 2015 and use it every time I go out. It is highly accurate and I love that it forecasts the time period for your body to metabolize the alcohol out. It has been a great tool and a HUGE eye opener for me.