TK is one of the few remaining full-service airlines around in Europe. So regardless of whether you're travelling in the front or back of the bus, you'll be served a full meal and there's free drinks to go with it. Food on TK
is generally quite good, as is the service and the standard of their equipment.
Taking public transport in Istanbul is of course an option, but in my opinion a waste of time since taxis are pretty inexpensive. Do keep in mind it's a very big city, and the little time you've got available won't allow you to see much. I'd suggest you take a taxi to Sultanahmet and go sightseeing in that area - the Grande Basar is a must. Grab something to eat at a Kebab place; it's both cheap and very nice. I wouldn't recommend a cruise on the Bosphorus this time of year, it will be pretty cold and probably windy too. Shopping, however, is something that might interest you; leather goods in particular is very good value and you can re-claim the VAT in the airport.
With a Gold card you can use the fast track lines at passport control, which is handy since the lines can be pretty long. The TK
CIP lounge is available to you, and as J-class lounges go it's one of the nicer ones. There's stuff to nibble on, but no full-service restaurant.
and Istanbul, you won't be disappointed with either.
From receips and radials over straight pipes to big fans - been there, done that, got the hearing defects to prove