Me and my wife have enjoyed staying at Cristal for 12 days. The location is absolutely fantastic, just a few steps from La Croisette and the Promenade. It is basically behind Palais Stephanie and the Grand Hotel. Just check Google maps and you'll know what I mean.
We stayed in room #101, at the end of the corridor, with large French doors facing the back garden. It wasn't sea view but it was a nice garden view and most importantly it was VERY QUIET. We didn't care about the view anyway (nor were we ready to pay hundreds of euros for it at the ultra-posh hotels on the frontline), because every morning we'd go on the beach anyway. And on the way, on the promenade, we'd have a double espresso and a croissant at our favorite kiosk, served by Pasquale & Salvatore, two Calabrese settled on Cote D'azure years ago. We'd have the best view there, overlooking the beach and the sea and best of all it was FREE.
Back to the Hotel!
The staff, and especially CHRISTELLE from Cristal (it has a ring to it doesn't it?) and Leonard were very, very helpful. Christelle took the time to listen to my problems with cancelling the car rental, to help us extending our initial booking and keeping the same excellent rate and generally being very attentive with us. The fact that she also had the rare talent of blushing at our jokes in broken French made her even more delicious and made us feel even more at home.
Leonard spent time describing the area to me, telling me about Mougins and Cannet and other surrounding destinations as well as little things about the daily life of residents of Cannes and the Cote D'azure in general.
Everybody we dealt with at this Hotel would go out of their way to help and assist us and if my broken French wouldn't work they fill the gaps in English. I am sorry I don't know all their names, but I assure you that if you go to this hotel with the right attitude you will be treated very well.
As far as the room goes, we were very pleased (and trust me when I say that we've done quite a bit of travelling). The room was large enough, the climate control worked properly, the beds were comfortable, the wardrobes had mirror covered doors, the furniture was practical and in good order, we had a small fridge/mini-bar and the bathroom was HUDGE. Our bathroom was all covered in rose/red marble with a shower over bath tub and a bidet! What more does one need from a hotel room? For us clean, quiet & comfortable was enough!
The lobby is quite posh, there is free internet access, a jacuzzi on the 6th floor and a bar and restaurant on the ground floor. We didn't use any of them because we didn't know how to get to the beach quicker, but they looked nice.
All in all, we highly recommend this hotel for it's cleanliness, quietness, staff, quality of rooms and of course for the fantastic location.
Dan, London UK

Roof spa isn't really what most would consider a spa so I wouldn't let that influence your decision. I didn't try the breakfast so I can't comment on that, there are lots of places that do a breakfast formula on nearby Rue Hoche for less than 10 euros so I went there. The view from the 6th floor breakfast room is nice so I guess thats what you are paying for. This is very central if you want to be near the bars and resturants of the Carre d'Or and the Croissette beaches, the old town is about a 10 min walk. The rooms lack style compared to some other Cannes hotels but my room was clean, my pillows fluffy and the air conditioning was quiet. Overall it was worth what I paid. This is the seventh hotel I've stayed at in Cannes ranging from 2 to 5 star.

We have just returned from a lovely stay at the Cristal Cannes, we got a great deal at only 50 euro per night for the room, hotel was well kept, if room a little dated very 90´s, but really clean, comfortable and quiet. 2 minutes walk to sea front, close to all the designer shops etc. I would return tomorrow for a good price but their standard rate is expensive, i would be hapy to pay 100-150 per night in summer and up to 100 off peak.

Fantastic restaurant 5 mins away Le Restaurant Armenien 82, La Croisette.
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The restaurant in this hotel is an excellent venue for lunch in terms of both the quality of the food and value for money. The menu changes daily and isn't extensive but it's well worth walking up off the beach.