I'm running at i5-2500K at stock (I know, I know...) with a Hyper 212 Evo cooler. I installed this cooler because my chip was running quite warm with the stock cooler.
Since I installed the cooler several months ago, I haven't had any stability issues, but I've been seeing higher temps in the past month or so. My temperature under normal load hovers around 50C, much as it did with the stock cooler. I got it up to 70C running Prime95, but couldn't get it above 56C while gaming (which is the most stressful thing I would ever actually do to it).