I read this very interesting thread because my wife and I plan going to Istanbul for her 50th birthday in May. We have already booked tickets for a long weekend around the 17th of May (which is the national day here in Norway) and will be staying at Hyatt Regency near the Taksim Square, as I understand.
Many people reccommend us Istanbul. Like: My cusin's wife was 2.secretary at the norwegian embassy in Ankara for a few years. Their daughter was born there. They have just 'fallen in love' with Turkey and plan moving there as pensionairs.
We were also thinking about going to Paris, but we have been there many times before and I had my Thinkpad stolen there last time. - A lot of fuzz with a visit to the Surte' as a climax. Further, we think that 6 Euro's for a cappuccino is a bit over the top (although the food is damned good in Paris and people are friendly).
Equipment-wise I will do it simple: I will only bring my Canon 1Ds II with a 24-70 mm 2,8L and possibly a 50 mm 1,0L for night streetlife. Today it is practically impossible to bring fast films with you without risking that it will be destroyed through security, - slower films are all right.
A M8 would be ideal - with my Carl Zeiss 25 mm 2,8 and a Leica Noctilux, but I have no M8 - and with the technical issues piling up around it I doubt that I will ever have one.