Is Mazda 6 a good/reliable car?

Ok so i had a 96 buick lesabre and it pretty much died on me in december so my parents bought me a new car but they told me to pick a used one....we went to a nissan dealership but i feel in love with the way the mazda looked. its black and a lil sporty. when we bought it the car had 36000 something miles on it and it is a 2007. the second day of driving the cold and hot gauge thingy was right in the middle but i had only been driving the car for 10 mins and my bf made me buy some antifreeze to cool down the car and he started saying that the car shouldnt be getting the hot that fast plus on top of that my dad was saying i should have picked a nissan and it would have been cheaper so im wondering if a made a good pick on the 2007 mazda 6.....and im a girl so i dont rellie know anything about cars so can you guys gimme some advance....??
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