It's been a couple of years but I always flew Turkish to Zagreb and transferred through IST. (I was flying from LAX but I'm sure SFO would be the same.) The 777 was the only thing available when I was traveling. I am going again in September and am looking forward to flying the 787. I haven't seen the new lounge, but the old one was spectacular!! We also liked to find a way to extend our time in IST either before or after ZAG. So, if you feel like something different, you may want to check out the Turkish Airlines forum. Have a good trip.