We enjoyed a lot... Great service, well trained smilling staff. You could feel that management is very professional.
Spa is great, relaxing, well equiped and good service.

Our kids enjoyed the breakfast buffet. The dinner buffet was also very good. The rooms were very complete with very nice sheets and mattresses although the climate control was a bit hard to figure out at first. We got one with a very pretty view of the bay. They had free Internet via cable to the rooms and our kids enjoyed this as well. The beach front was close and mildly interesting though not fantastic. Visiting Istanbul, specifically the Hagia Sophia church, Basilica Cistern in the Sultanahmet area was excellent. Transport by taxi is quite expensive i.e. USD 70.00 for one way from Taksim Square to Buyukcekmece. Buses take much longer but are much less expensive.

We had some great days with colleagues using the conference facilities at Eser hotel.
Very friendly and helpful staff though english language not so good.
Wonderful rooms nice soft beds. But smell of cigarette in some rooms
The food in the restaurant was very good. Served by nice staff.
The Spa was excellent.
When one of us needed medical help the hotel provided quick assistance.
We can recommend this hotel!

Do not hesitate to book if you are on a business trip to the area. I have been to several fairs in Tuyap Expo Center and stayed at several hotels. They were either expensive or lousy hotels. And don't get the idea that by paying much you get better service.
Dedeman is a very well known hotel chain in Turkey (not so much by outsiders), this specific one is new in the chain. The new blood brought quality to the area, will book again in my next visit.
Ask for upper levels so you can have a great sea view, also try fine dine roof restaurant. Fantastic view and great food. If you travel there in summer, the public beach is 50 meters walk, but it can get very crowded. Be sure to have a walk in Büyükçekmece Bay, sunset is exceptional. Several shopping malls, one historic bridge made by "Mimar Sinan", an aquapark with nice rides, some fish restaurants by the bay and some restaurants that serve local food from different areas of Turkey is all to see. I have heard of a complex with jeep driving ranges, water sports, picnic and BBQ facilities by the lake but never been there. Maybe I will try it next time.