We often use the interjection Man! (not addressing anybody in particular) when we're taken aback by something - in a good or bad way. So it almost always precedes a compliment, complaint, or observation - as in the above example. It's always the most stressed word in the statement and can be stretched out for emphasis: MAAaaaan!

Optionally, you can invert the subject and verb that follow: Man, is this a delicious pie! Man, is it hot in here! (These aren't questions, so don't give them an interrogative intonation!) You can just as well say: Man, this is a delicious pie! -or- Man, it's hot in here!

It can also be used in negative statements: Man, are you stupid! (Man, you're stupid!) in all these examples, it's the same as saying: "My God, I can't believe how... someone/something is."