Stayed for the first week in June, weather a bit changeable (June one of wettest months apparently). Only 150 metres walk each way = Nessebar Old Town (Heritage site) to the left and a great Nessebar beach to the right. If you don't want to pay 30 levs (about £12.30)for the beach equipment you can walk past it and just use the beach.
Food at the Sol Marina Palace on "all inclusive" was plentiful and we enjoyed it. Hotel wine and beer might not be to everyone's taste.
We were on the 4th floor, on the front, looking out to sea and it was great, we saw Dolphins feeding right in front of the hotel on one afternoon. Another side of the hotel looks out over Nessebar old town, which would be equally good. However, rooms to the other side would look out on apartments.
Trips to Bergas, Sozopol and St Vlas were good, However, Sunny beach was a bit rough in our view. The beach is great, but the resort caters for the younger, wilder sort, rather than us, an older couple.
Overall, we had a great time, Hotel ideally placed, all inclusive worked well and weather was sufficiently good to get on the beach for 3/4 days out of 7.