I've never seen PIPs work out well, although all my observations are from outside the manager/PIP-ee perspective and perhaps my sample size is not large enough yet. One employee managed to meet the demands of the PIP but only at the expense of dropping all other (not documented in the PIP) tasks, an extreme case of "what gets measured gets managed". Overall, they got to stay on but it was detrimental to the team they were in.

The more savvy people started applying at other companies the same day they received the PIP, since it was clear to them they would have to work significantly more for no increase in salary and they perceived the attainable effort/reward ratio to be better elsewhere. In one case this led to hilarity when the CTO had instructed the managers to PIP at least one of their team members "for morale reasons" and it ended in more than a third of all devs leaving the company in the next two months.