I had an amazing trip, the sights are incredible and the tour is very well organized and run. You need the stamina and willpower to get through all four days but it is completely worth it. Acclimatization and a reasonable level of fitness is needed but it is an excellent trek, the food is great and the tour guides we had were very competent, fun and encouraging.
Downside are the toilet facilities which are basic and the showers which are cold, but this should be expected with this sort of hike. If you have a cool group to walk with and a positive attitude then it is an amazing experience in an unforgettable location.