I just did a transit through the new IST airport, and the facility itself is a massive improvement over the old one, but as some have commented, the distant location from the city is also a huge negative if you want to go into the city. That was a breeze from the old airport, but clearly not from the new one. I used to love to go into the city, particularly the Sultanahmed area when connecting f through IST and specifically looked for itineraries that allowed me to do that. Not anymore, unfortunately.

Another difference I noted was that at the old airport, my connecting gate seemed to always be quite close to my arrival gate, but on my first experience with the new IST, my departure gate was a long, long way from my arrival gate. It did have the effect of letting me see most of the airport in moving between arrival and departure gates.