This is not directly related to W Istanbul, but in response to mecabq's earlier comment on car service (airport transfer) in Istanbul.

Mecabq's right about not getting the service from the hotel as it's ludicrously expensive. I used the airport transfer service provided by Backpacker's Travel Agency in Istanbul for a fixed rate of 25 Euros (from Hyatt Regency near Taksim to Ataturk airport), I think it's only 20 Euros if your hotel is in Sultanahmet. http://www.backpackerstravel.net/index.php?pid=1&id=45

I learned about it through Turkey Travel Planner. It's no-frills, but reliable and inexpensive. Better than a taxi and you definitely won't have to worry about being scammed by taxi drivers.

I used the service just a few days ago on May 1, which was Labor Day in Turkey. There were protests and many roads near Taksim were closed. My driver was smart enough to arrive early before the roads were closed, parked his car nearby, came into Hyatt Regency's lobby to pick me up, carried my bags and we walked a couple of minutes to where his car was parked, and delivered me safely to Ataturk on time (and yes, drove carefully through the protesting crowds, it was straight out of a movie....). I can't tell you how much luckier I felt than the hotel guest next to me who had to haul all his luggage and walk all the way to Dolmapache Palace to get a taxi (as, by this time, no cars were allowed to go near the hotel).