Stayed here for 6 nights during a conference, which was held at this hotel. If you are going to stay at the hotel and don't venture outside, the hotel is just fine, although overpriced. The restaurant serves pretty good food for dinner; their breakfast is excellent and it is included in the room rate. There is even an Irish Pub with lots of LCD TVs and a huge projector screen where we watched the games from FIFA world cup. Their outdoor pool is very nice, although you can hear (but not see) a busy road from there. My friends told me that the spa services (esp. Turkish bath with massage) are superb, but be prepared to pay about 3 or 4 times as much as you would for a similar service at an Istanbul hamam.
The biggest problem with this hotel is that there is absolutely nothing within a walking distance and the only available transportation is a taxi. Theoretically, one could use free shuttle buses that are operated by Bilkent University, but the bus stop is quite far away and the service schedule is nonexistent. At best, the shuttles to the city center run once an hour. A taxi ride to the old part of Ankara would cost about 40TL.
