The overall rating is too fixed. On good nights it's very good, but I've had more than one average experience here. Bear in mind that once in the Al Bustan, unless you have your own transport you're a captive audience. Taxi into town looking for a cheaper meal runs OMR5 and up (each way) and outside the hotel the only restaurant I know of nearby is the Blue Marlin down at Bandar Al Rowdah marina, which has pleasant, helpful staff and decent if uninspiring food, but - trust me on this - none of the glam you'd expect from a place in the Gulf with 'marina' in the title. Nothing within walking distance, full stop.
Al Khiran is located at the rear of the Al Bustan Palace, with views to the palm gardens and the pools between the hotel and the beach. There are tables on the outdoor deck, which are very nice in the cooler months; best of luck in summer with high temperatures and humidity even at night. Any of the window tables will give you a pleasant view while you eat. The restaurant isn't so deep that you'll never be stuck without something to look at, and the tables aren't so close together that your elbows are in someone else's soup. The centre of the room is taken up with food stations for different cuisines or different courses, depending on what's on offer.
No surprises on the self-service breakfast menu (7-11 in summer) : cooked English/American style (including pork and bacon); cheeses; cold cuts; breads and pastries; all the Arab options you could hope for; fruit; plenty of fruit juices. No congee yet, though. The serving staff are usually more nimble at breakfast, checking up on your beverages and refilling quickly. Best to have it as part of your room rate; if not it tops OMR14 a head.
Dinner is served between 6:30-10:30 every evening. They recommend reservations but I ate late, after 9 every night I was there and the place was never busy. Every evening is a different buffet, or you can order a la carte, which I've never tried. The best I've tried are the international night - steak/chicken a centrepiece, along with half a dozen alternatives - and the Asian night, which is consistently good. I've yet to see a night when some form of seafood didn't feature, but I'm surprised it doesn't feature more heavily when the beach pavilion is closed, as it is until early August. There's always a good spread of sweet desserts, usually including an ice cream station.
Per head around OMR21, but drinking only water; add alcohol and you'll need a friendly credit card company.