Certainly not criminal, but I was on a county commission which put me in the position to watch people litigate pro se regarding land use suits in California. And I would occasionally be in court waiting for a final declaration (that for some reason had to be in the courtroom.) There were plenty of people who successfully defended themselves pro se, but I don't think I ever saw anything more exciting than someone bringing in documentation clarifying they weren't the owners of a property on which some crime occurred (apparently the county's GIS system is not the local sheriff / prosecutor's strong point.)
I'm not trying to imply you should represent yourself on a felony case, but at least in California in the past, people have successfully had cases dismissed when they appeared in court, representing themselves with documentation the prosecutor should have looked at before filing the case.
Could you tell us more about the source of your experience please?
> pro se works more often than owenmarshall implies,
And there are very well documented cases where a pro se defendant gets themselves into bigger trouble.