I had CO2 done about 8 years ago when I was 22. I was hoping to primarily treat some mild icepick scars and secondarily freckling.
The procedure itself was not bad but immediately afterwards, my face was red and burned. The doctor gave me Aquaphor and told me to apply it religiously until the skin had peeled away on its own. After about 7-8 days, most of the skin came off and underneath was new, fresh, pink skin. The pink color went away after another week or two. The recovery period was long and difficult, made more so by the fact that my doctor did not give me proper warning. It was hot like a bad sunburn and a bit painful at times.
While it cleared 95% of the freckles, it was not as effective on the scars. In fact, I am not sure that I saw any improvement in the scars beyond smoothing out the skin a bit. My scars were relatively shallow. The hyperpigmentation within the scars remained the same.
My doctor was good and bad. He seemed to perform the procedure well but was lax on patient education, communication and follow-up.
CO2 might be more refined today but it is still a big undertaking. Although a lot of doctors say it is the best treatment for acne scars, based on my experience, I feel that it is best for extensive sun damage, mottling, and hyperpigmentation. And always as a last resort.
I would not do his procedure again although I was happy with the freckle removal.