There are 2 downsides in this hotel : you can feel / hear the metro trains passing since the hotel is located above a station of the RER and the rooms are beginning to show their age (nothing dramatic though).
There are more upsides though, the rooms are large , decent badroom size as well. The restaurant was a pleasant surprise - a very nice meal, for a reasonable price.
The hotel has it's own parking, and the RER (subway) entrance is right next door, which will bring you to the center of Paris. Also the offices and shops of La Defense are at walking distance.
The hotel staff was very friendly and helpful .

This hotel was the first on our France honeymoon trip. After a little confusion with the other Mercure Defense hotel, we ended up here where we were graciously greeted at the front desk. We had mentioned ahead of time that this was our honeymoon, and they were wonderful. We were upgraded to a better room and there was a beautiful plate of fruit on the table. We opted for the buffet breakfast the next morning and found it full of delicious fruit, pastries and meats. We ate a lot of such breakfasts while we were in France and this one was definitely one of the best.
It's true that this place is in the financial district, so there's not much around on the weekends, but we did manage to find a great little italian place just down the street.
This hotel is also really really close to the subway station, which makes it super convenient for getting around. We would definitely stay here again.

Ok so it's not handy for tourists but we were on a Cosmos tour so had the coach to travel into the tourist spots and there is a train station right next door! The rooms are huge I stayed in 108 and it had a separate door to the bedroom and bathroom it was clean ... The breakfast catered to all tastes. The poor barman didn't really know how to make the drinks we ordered but was happy and muddled through with a smile on his face which is always nice...