This is a review of the restauruant only. No idea what the hotel is like.
Whilst Nikki Beach is fun, it's also very young so if you are 30+ then Tahiti Beach is much much better. The food is excellent, the service is also excellent, the music is excellent and the waitresses / waiters tend to join in the fun.
The first lunch sitting tends to be a little bit more subdued but the second sitting....that's when a party across the whole restaruant inevitably breaks out. Lots of chilled people of all ages and varieties dancing on the tables, drinking, mingling and generally speaking having a great time!!!
It's not cheap (Nikki Beach is more expensive though) but it's alwasy fun.
Probably better to go with a group of 6+ or so than as couples but, hey, that probably works too as you always end up chatting to everyone else.
Definitely best to reserve a table in peak season and I would also suggest a table in the front part of the restaurant (by the beach) rather than the back.