I've flown Saudia domestically in Saudi Arabia during trips there. The planes are clean and generally comfortable. It's easy to secure exit row seating - and Delta status will give you lounge access. The lounges are small, but I quite like the amenities.

The boarding process is odd with "families" able to cut to the front.

There is no alcohol served on Saudia.

All that said, Jeddah airport is rather awful. No jet bridges, unorganized check-in and a dated building. The staff can be uninterested, but have recently made a better effort. The airport generally makes Newark look appealing.