We booked a half board special from the hotel's website at very attractive rates and got a nice room with great sea view. I think it opened only a year before and everything is state of the art.
The staff was very professional, friendly and helpful. The breakfast and 4 course dinner was good but not outstanding. The "design" bit is pretty much limited to the lobby, the rooms were rather typical hotel rooms.
Try to get your room on 3rd floor or higher for better views.

A pleasant surprise, large rooms well furnished and very clean. Great value.

We saw a few of the mixed reviews but were impressed that the hotel's management always responded to each in a positive way. This is the sign of good management who wants to improve things and takes into account each person's opinion.

We found the hotel to be of very good quality in a very good location close to the center of the town. The breakfast was a very good variety and we never sat longer than a few seconds before someone would appear with a pot of coffee and a pleasant "Jutro!" Parking is convenient and no problem if you are able to secure one of the hotel's spots. The staff is quite friendly and always happy to respond to any requests and in fact went above and beyond on a couple of occasions.

We would absolutely recommend this hotel and stay here again.

We spent 3 nights at the Astoria in Opatija. A very pleasant hotel and very attentive staff. Recommended.