I stayed at Holiday Inn Express (Oklahoma City North) during a recent business trip, and was extremely pleased with both the facility and the customer service. The entire hotel was exceptionally clean; my room was really beautiful, and very quiet. Great place for getting work done during the day.
The hotel is far removed enough from the city to be quiet and easy to get to, but close enough that you're within easy driving distance of any location you might need to get to in the metro area.
I highly recommend this hotel, and will be a return guest anytime I'm in OKC.