My daughter had strabismus surgery when she was 8. She had been patching since around age 2 and never got better. The surgery itself wasn't that big of a deal... and the worst of the pain was over within 36 hours and most of that she slept through because of the general anesthesia. I think the very worst was the next morning after. The stitches on the muscles inside the eye did bother her for about 5-7days until they had dissolved (she also has congenital nystagmus so her eyes are constantly moving) and she was out of school for 2 weeks as a precautionary measure. Tylenol helped lots and I gave it to her whenever she wanted (every 6-8 hours).
Would we do it with what we know now? definately... probably would have done it sooner. Also.. not that this could happen, or even might happen, but my daughter's vision in that weaker eye went from 20/200 to 20/80- 20/100, huge improvement.