I have seen many others on this thread saying that John Piper was their introduction to the Doctrines of Grace, the Puritans, Calvinism, etc.
Well, I discovered him very early on in my dive into "reformed" theology, and it was a great hinderance that almost completely repelled me away from the all of the above.
I found reformed theology because I was desperate looking for any vein of Christianity that still practiced church discipline. So, that led me quickly to Reformed Christianity, Calvinism, the Doctrines of Grace, etc. And while trying to understand the Doctrines of Grace I found John Piper.
Growing up Pentecostal and coming to see that it was a false system of worship, with terrible doctrine, I immediately found John Piper's emotionalism very repulsive. That was even before I learned that he was a continuationist. So, it did not surprise me at all to find out that he promoted men such as Lou Giglio and the likes of him. I am glad that this did not completely deter me, though it almost did.
So, say what you will, but for me, it ain't worth the trouble of the bones.