The practical application of an obviousness challenge is simply this: would a person of ordinary skill in the art find the claims to be obvious, in view of the prior art in front of them.
The biggest challenge with the presentation of an obviousness argument at the PTAB is the page limit. It's the fact that a petitioner has only either 60 pages or 80 pages to explain their story and it sounds like a lot of room, but when it's time to sit down to write these challenges it's very tight and that's the biggest single challenge of presenting an obviousness argument.
How do you win an obviousness challenge before the PTAB? First, extensive and prior art searching. The most powerful challenges tend to be those that present prior art, patents and printed publications that were not considered by the patent office when it examined the original patent. Then, you get great experts; the judges at the PTAB want to hear detailed explanations from highly-qualified individuals. The objective is to present different combinations of messages that approach the problem from different ways.
Then you present natural combinations: for example, it would be good to present a series of prior art publications or patents that fit together smoothly and nicely, and you can explain them in an elevator speech, that way that natural combination will win.
The best chance for a petitioner to win on obviousness challenge is before the PTAB. You have to make the right strategic choice as to the prior art you're going to present. Don't present combinations that are strained or difficult to explain. Present natural combinations that fit together like pieces of a jigsaw puzzle.
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