I was an Istanbul 2 years ago during a Mediterranean cruise...It was interesting to see (then again after about the 3rd Mosque they all start to look the same). The world famous "World Bazaar" was highly touted for the excellent shopping. I found it to be nothing but a sea of junk as far as the eyes could see, with annoying sales people at every turn hounding you to buy a rug. I was there in August, and it was insanely hot. I basically left Istanbul with the feeling that if I never return to the city again in my entire lifetime that would be just fine with me. It is one of the world's largest cities, a cultural and ethnic melting pot, with architecture that dates back thousands of years. So, from a historical perspective, it is an interesting city, but so crowded and not particularly clean in many areas. After about 3 hours wandering around seeing the sights, and escaping from a rug store where I somehow ended up getting talked in to a set of $300 plates by a savvy salesman --- I think they may have spiked my "Apple Tea" - LOL!) I couldn't get back on the ship fast enough.
We did go back into the city at night to checkout a few clubs. It was okay, nothing I could not have missed. I will actually be there again this August on another cruise. It's debatable if I even leave the ship at that port, but maybe I will give it another look and gain a better perspective, however I won't be setting foot in any rug stores