I will rate my experiece in this valley (quebrada in Quechua) independant of the only cultural aspect of the WHS. For me the natural/ landscape experience was more fascinating than the cultural aspect which is also interesting.  
 
Already the ride from Salta or Jujuy into Tilcara is a highlight. While driving uphill the landscape changes from green hills, forests and meadows into a dusty, red- brownish mountain landscape which sees mainly huge cactus growing. Maybe it is because I haven't travelled such a landscape before that I was quite happy but also others on the bus liked what they saw during the ride.  
 
Tilcara is quite a picturesque town. My family thought I'm in the Wild West when I have sent them pictures. We visited the Pueäcará de Tilcara within 1,5 hours in the evening of the first day which was sufficient. There is a flyer with some basic info available in English which doubles partly with some information signs in the fortress, that is more an ancient village than a defensive structure. Additionally there are guided tours in Spanish, which we didn't take. In addition to the historical aspect of the site I found the archeological controversies that happened here in the first half of the 20th century the most interesting. In short archeologists rebuilt parts of the Pucará (fortress in Quechua) but with wrong techniques and built a road that destroyed parts of the archeological site. Finally others build a monument for the archeologists within the site which again destroyed parts of the original remains. Quite shocking I found. The archeological museum in town is a nice addition to the Pucara. Best was a 22 minute movie with English subtitles on the history of the Pucará. There are also displays of the findings of the site. Many of the rooms were closed for renovation but it was still interesting. As recommanded by Frédéric we visited the Garganta del Diablo which is not tge same thing as in Iguazú obviously but it's an impressively thin and steep gorge with a nice natural waterfall a few hundred meters up the valley. Finally I can really recommand the two tasty restaurants with great ambiance Khuska and El Nuevo Progreso. In the latter you will meet all the other Gringo tourists ;). 
 
In Humahuaca there is nothing much to do than strolling ten minutes around the town center. We took a tour that you get "attacked" with once leaving the bus to a mountain up the hills that should contain 14 colours which is more or less correct. Probably it's even more impressive with sunlight. On the second day we visited the village Uquía which is in between Tilcara and Humahuaca. As it was the day of elections everything was closed meaning the church and the Quebrada de las Señoritas. One inhabitant asked us to respect to not visit the valley which we ignored like many others. I find it a bit annoying to close down nature without any infrastructure just because no one has time to get the cash from the tourists (not sure if there is any other good reason to close it). We visited the "Amphitheatre" at the end of the slim valley of the 13 curves. It reminded us a bit of the Talampaya tour walking through red, narrow, high cliffs. In the amphitheater a security woman caught us and asked us to leave the park. We pretended to not speak Spanish but followed her request. At the conjunction to the second branch of the valley, we waited 5 minutes in which the woman seemed to be busy throwing out other tourists. So we decided to be a bit more disrespectful and visit also the Quebrada de las Señoritas branch with thin and steep, white and red rock pillars that on opened days can be further explored with a guide all the way into caves. We followed another loud announcement of the security woman from the entrance point of the valley without seeing her again while returning. Instead a few new tourists passed by while we left. It's really a recommandable spot of nature and we are happy that we have ignored the local resistanxe to not visit on this day as we would have missed a spectacular place and we didn't cause any harm. 
 
All in all the only really cultural place and by this WHS place we visited was the Pucará and the related museum in Tilcara and maybe you could count on the local lama meat I ate as well as cultural. This however would only be a 3 star rating for me. However with the natural sites in the valley my experience was a 4 star experience which is how I try to rate the WHS. I can really recommand the valley and spend some days here as it's exciting, beautiful and relaxing I find.