The Good:
The hotel has a beautiful private beach.
The rooms are nice, but far from luxurious. The breakfast and dinner buffets are excellent. There are family-friendly activities scheduled throughout the day. The pools are nice and drinks are cheap ($3.00 USD for a gin and tonic).
The Bad:
The building is starting to show it's age. Both my room and the room next door had ants. In their defense, the cleaning staff tried their best to get rid of the ants, but they just kept coming back. Similarly, the "pub" could use some serious upgrades (lopsided pool table, wobbly plastic chairs, very limited drink selection). My wife went to the spa and was very disappointed. Her masseuse didn't even leave the room while she was getting changed. The final thing to note is that this hotel is not in Sousse - it's in Hamam Sousse, which is about 25 minutes north of Sousse. That's not necessarily a problem, but if you plan on going to the Medina or checking out the nightlife, be prepared to drive.
Overall:
If you're looking to be pampered in a 5 star hotel, go somewhere else. By North American/European standards, I'd say that this Iberostar is equivalent to an average 4 star hotel. On the other hand, if you are just looking to spend some time at the beach/pool, eat lots of food and drink cheap liquor, this is a good option. It's also quite kid friendly. I paid $75 USD/night (late April/early May) for a double room with breakfast and dinner included and thought that it was a fair price.