Pros
Writing applications that interface with more than just your computer can be awesome and rewarding, and NOV (Anderson, TX) is well-versed in how to do it on an industrial scale. You will definitely learn a lot from the in-house talent on how fracking equipment works, as well as how to develop software for it. There's also a lot of caring attention to detail that goes into their products (both in terms of the physical units and the software itself). Beyond that, this is a pretty typical oil/gas type job: things are chaotic when the oil industry is booming, and slow when the oil industry is slow.
Cons
Compensation was slightly lower than what you can get elsewhere (though this is offset by the lower cost-of-living in the area). Definitely not a job for someone seeking work/life balance as their main priority, as you will occasionally be putting in long evening and weekend hours (mainly because that's just how the oil industry is). Not really the place to work if you are looking for career advancement in software development. Nitpick: Due to the looser corporate structure with NOV facilities, information from other departments (or sometimes even corporate) is occasionally hard to come by. They have taken steps to change this with richer internal websites to help share information, but nitty-gritty details (e.g. available servers, software licenses) remain more elusive.