In by experience, 220 pretty much cleared the Step I hurdle. What I mean is, if an applicant had +220 then he/she is pretty much in the same boat.
Dude with 223 definitely has the mind to pass boards in four years so he is essentially on the same footing as Mr. 252 after the first round of screening.
Screening being, does the applicant have the test taking skills to pass boards someday. My program has a tremendous record of board passing. We are confident that we can train a person to be a good anesthesiologist and to easily pass the boards. However, starting with an aptitude to pass standardized tests definitely helps.
I am just throwing 220 out there as the arbitrary number that shows 'no difficulty with standardized tests'. Are you out of the running with less than that? Absolutely not, you just better show other skills and a work ethic to prove that you can put in the work to learn what you need.
We look for people who are good people, hard workers, fit in well, team players. In my opinion, it is ridiculous to base applicants purely on board scores. It is definitely a factor, and let's be honest, a pretty big factor. But it should only be one tool in the screening process.
You can definitely get in with scores much lower than that, but that is pretty much the 'get your foot in the door and knock their socks off at the interview' number.
Don't be discourages with scores much lower, just get busy and make the rest of your app outstanding.