I was surprised to find this forum didn't have a thread for this great hotel, so I thought a starting point would be good. Early threads on FT suggest that the hotel was not participating in SPG - I can confirm absolutely that it is.
The hotel lists 23 floors; there are two SPG floors, two Club floors and two floors offering the Towers. I booked a standard room for SR400 (no status with SPG) and with a little help from Saudi Arabian Airlines, was delayed till 4 am - and this led to an upgrade past the Club right in to the Towers floor. ^ For those arriving - the airport is a LONG distance form the city - perhaps, 30-40 minutes at crazy break-neck speeds. Taxi fare will be SR60-100 depending on your haggle skills.
Room is average size, but has a very spacious feel with a large window and ocean view.

Decor is very nice with two comfortable chairs, foot stool, writing desk with hard chair. There is a good coffee machine - and the blend used is top rate and will satisfy a European taste, and with a little more water will satisfy Americans too.

Amenity is fresh and ordered by phone - choice of chocolate strawberries/oriental pistachio/fruit basket/stuffed dates. Two bottles of water.
There is a good widescreen TV, iPad dock (good sound) and a Corby trouser press. There is an iron. The Towers floor also allows for 3 items to be pressed on arrival - so I sent my airline rumpled shirts down at 4 am and they were back at 4.10 am. ^ Bed is firm but comfortable with 4 pillows with firm and soft - there is also a pillow menu available. The room is well lit with a selection of spots, desk and bedside lamps, floor lamp and lights over the framed pictures. The mini-bar is well stocked and reasonably prices, as is common in Saudi Arabia, but has no alcohol, needless to say.
Bathroom is smaller than you might come to expect, given the spacious feel of the room, but perfectly adequate, nonetheless. Full set of the usual amenities, razors, comb, shoeshine, mouthwash, cottonbuds, emeryboard, etc. Bath, shower bidet and toilet. Also there's a good speaker in the bathroom, so you can croon along with your iPod while in there.
Pool is nice 1.5m (about 4 feet) deep and uniform across the whole area, well maintained but perhaps a little warm. That said, it is 50c (122F) outside today, so you take what you can get.

Changing rooms are terrible - the norm in Saudi in my experience - tiny, cramped, poorly lit no seats or lockers. Clean though. 4 changing cublicles, 4 toilets and 4 sinks. There is an outside bar serving cocktails and a lifeguard on duty.
Lobby is spacious and there is a coffee shop called Vienna, or something similar, with a good menu, including all day breakfast (the regular restaurant breakfast finished at 10.30), snacks, snadwiches, cakes and the coffee is very very good. Staff were polite, well trained, helpful, but moving on Saudi time, which is way too slow if you're hungry.

Full resturant in the basement overlooking the pool garden; ladies and gents spas.
I have not been to the Towers lounge due to committments, but if I make it up, I'll report back.
Recommended?
Hell, yes.