We loved staying in CasaLoBueno! I was recently in Istanbul with 7 fellow students, and we stayed in two apartments in this listing (I think #4 and #6 in the building). Everything was absolutely perfect. The accommodations were spacious, comfortable, and clean; we had four people in each apartment and had more than enough space for everyone. Izel arranged for transportation to and from the airport for us, and when we arrived, he met us at the apartment with keys, welcome manuals, two local cell phones, and two Istanbulkarts (local transportation cards you can use on metro, tram, and ferry) - this was invaluable for our stay. He checked in again throughout the week, and met us to help arrange our departure.
Perhaps most importantly, the neighborhood and location were simply ideal. The apartment is on a small, adorable street with restaurants, coffee shops, and hostels, less than a block away from the stunning Galata Tower. It's less than 5 minutes' walk up to the bustle of Istiklal Street, or down to the Galata Bridge that will take you to Sultanahmet. Beyoglu was the perfect home base for our first time in Istanbul, and we would love to stay here for return trips! Definitely book this apartment.