I (with family) was at Mercure Grand Jebel Hafeet for the weekend starting 27 Jan. It also happened to be my 9th wedding anniversary. This place looks always fully booked for the weekend, which explains the increase in prices during weekends compared to week days. The best part about the hotel is the location, set on a sprawling area at the edge of a cliff in a V-shape. All rooms would then give you a view of city around 1200ft below. Unfortunately, it was misty all around so the view was not the greatest. The check in was smooth and fast, no hassles. Of course i had to book online to get the rooms (which was advised by the reception staff). Apparently there is a quota for online booking, so even if you don't get reservation through email/phone, try doing it online.
They have a nice pool area with kiddie play area as well. There are facilities like Gym, massage parlor, pool table/squash court/table tennis/mini golf, you can borrow the accessories from the recreation center and return them back once you finish. The gym is well equipped.
Us being veggies, the number of choices for dinner was bare minimum but adequate. So no comment on dinner.
The breakfast was continental, adequate and tasty.

The best thing was the view, nothing like it. I guess if you are there on a clear day the Sunset would be a marvellous sight. They have an observation desk in the second floor which is a good point to watch the sights and sunset. All in all nice weekend break for us from Abu Dhabi.

Spending 8 days in Emirates, We decided to spend 24 hours in Al Ain. But my comment on this city is that Al Ain is better to skip if you are visiting Emirates.
This Hotel is in a fascinating location, but 20 minutes driving from City. Big room and very big bed, that's all. attention: it is not located where trip advisor flag is pone.... this is the po box address!

We only spent one night there, coming from Oman on our way to Dubai. The location is fantastic though out of the way. It was fine with us as we did not intend to visit Al Ain, just to rest for the night. The price seemed cheap but that was after 10 days in Oman, where accommodation rates are very high. The room was spacious enough with a fantastic view. Our kids enjoyed the minigolf and the slides at the pool. Great for a short stay, but would not stay there for a longer vacation.

We stayed here with family for 2 days and we feel that we should have planned for more time. Hotel is located on top of the mountain with awesome view. Besides normal facilities which all hotels have, this one has pools and water recreation for all age groups which is nicely maintained. Large pool with bar was good. Hotel staff was prompt and courteous and were keen to arrange for local taxis for roaming around as hotel is 30 minutes away from city. Room was good but balcony was small. Food was OK and could have been better.

Overall would recommend this and would definitely plan to stay again.