OKC has been a boomtown due to the fracking boom. The metro area is up to about 1.5 million people. Real estate is cheap because there are no land barriers and developers can keep sprawling out onto cheap farmland. And up until about the late 1990s, no one wanted to live in OKC.
Because of the energy industry boom, everyone in OKC is from somewhere else. That somewhere else is more often than not Texas. But people get pulled into OKC to work the shale formation from all over.
OKC is a southern city. It is basically Dallas' mini me. People are pretty laid back and have good senses of humor. The state is very conservative and most people you will meet in OKC are in the oil and gas business. But you will also meet plenty of normal center-left to progressive people in OKC.
There is plenty to do in OKC. Lots of concert venues from small to large (U Okla is just south in Norman if you want to hang with the kids). Plenty of decent restaurants (and real Mexican food). You are about 3-4 hours drive to DFW if you need to see an NFL game or go to a symphony concert.
OKC is hot as F in the summer with a good 3-4 months of 90+ with plenty of humidity. OKC is right on tornado alley. And most homes in OKC have no basement. Make sure you have comprehensive auto insurance as OKC also gets some pretty massive hail storms. The city is actually very green with decent amounts of rainfall, but lots of sun.
If you need to be in the mountains, the Sangre de Christo range in NM (Taos, Angel Fire, etc.) is about 8 hours drive away and most of the ski areas in CO are 12 hours. Hot Springs, AR is a day's drive and has nice camping, lakes, rivers, etc.
You could do a lot worse than OKC. Between OKC and Seattle (my wife's family is in Seattle), I am not sure that it is worth it to be in Seattle and be broke versus being in OKC with the good ol boys, mega churches and strip malls but having enough money to go out and enjoy yourself on the weekends.