Had it done bilaterally about 8 years ago. The best spent money of my life.
The danger in the first days is that, with some blow or over-pressure due to effort, the flap could potentially move out of place (you know it is not sewn up but only gently placed back in the proper alignment, do you?). Obviously a misaligned cornea wouldn't be good for your future vision. Avoid scratching or rubbing your eyes also, by the way.
After these first weeks it starts to heal and get "re-welded" by itself so the dangers fade away.
I've never had any complication afterwards and had 20/20 vision since.