I visited Ephesus on a two-week group tour of Turkey in July 2018. As everything was organized, I have done really few researches beforehand and I was happily surprised to discover such an impressive site! We spent two days in Selçuk. We had free time on the first afternoon and I used it to visit Saint John's Basilica, Isa Bey Mosque and Ayasoluk Kalesi. The second day was spent for a group tour to Ephesus, Artemis temple and Şirince (not inscribed) and a self-guided walk to Grotto of the Seven Sleepers (buffer zone) and House of the Virgin Mary.
Inscribed sites closer to Selçuk (Saint John's Basilica, Isa Bey Mosque and Ayasoluk Kalesi) are interesting but far from breathtaking. The Basilica was a very important site for the history of Christianity, but only a few columns and foundations remains. The same apply for Isa Bey Mosque. I know it's an important place, but the visit was not memorable. Selçuk is a nice city to visit. Ayasoluk Kalesi gave me the same feelings of a historically important place where few remain. All these three sites can be seen in the photo background. I really enjoyed the ruins of the aqueduct with its numerous nesting storks!
Ephesus old city is by far the highlight of this WHS. The library and both theaters are especially worth mentioning. Having a guided tour of the site was great. There's not much to see of Artemis temple. A single column made of many pieces remains and, again, storks nest on it (photo). Şirince, though it is not inscribed, was an interesting excursion for Selçuk. Learning about the population exchange between Greece and Turkey was great.
My walking self-guided tour to Grotto of the Seven Sleepers (buffer zone) and House of the Virgin Mary was fun as the views on the landscape are beautiful. Otherwise, both sites are, at best, boring. Only a few uninteresting brick constructions remain at the site of Virgin Mary's House. I don't believe neither of them should be within the core zone. You shouldn't take time to go there, unless the pilgrimage is important for you.
In sum, Ephesus is an amazing site and well deserve its late inscription on the list, but most of its OUV come from only one of the components I visited.