We booked a "de luxe" room, but got a "standard" one. (We were not quite sure about our order details and were too tired to argue on the spot, but the next day the receptionist said he would have changed rooms, had we let him know. He immediately offered to refund the price difference, too, or a free upgrade next time, though.)
Coat stands, racks, hangers in addition to the wardrobe please! (No place ever has enough of these, to hang towels and other stuff to dry or vent etc.)
Some noise from the neighboring room (but this is, again, a general motif with most of the places everywhere).
Without a car, traffic was slightly inconvenient: we needed to repeatedly walk a lot to and from the bus stop. We also couldn't quickly find a nice nearby place to go and relax a bit with a coffee or beer. (But Cagliari is not for getting stuck near hotels anyway, so this was not a big deal after all.)
Lovely, helpful, professional staff (the guy at the reception desk, and also the guy serving at the breakfast), great English, too; a real relief. Breakfast was OK, the coffee & cappuccino were great!
Wifi in the room.
Nice internal garden, must be lovely in the summer. (We were there in March.)
Location is far from the city center (closer to the airport, though), but has good public transportation (bus 31). The suburban neighborhood was kinda' interesting, even pleasant at some points.
It's definitely best going there with a car; parking seemed to be no problem, unlike in the city center.