I visited in December 2017 and was worried about altitude sickness, but was quite rushed the days before the trip and didn’t have a chance to get sickness pills from my doctor.
I personally didn’t feel any symptoms, and neither did my friends. We’re all active and healthy people in their 20s.
The only real impact was reaching a shortness of breath much more quickly: hiking and such was certainly a lot more difficult than I’m used to at sea level. I had the same type of experience ski touring in Colorado; never really feeling satiated from breathing during vigorous activity.