My family & I stayed here recently over 5 nights. I chose 3 Sis based on the strengths of its reviews on Trip Advisor & its location, within the old city of Chiang Mai.
Perhaps my expectations were set too high by the reviews here. but I felt slightly disappointed after staying there. It is a great place to stay, and its pricing (B1300 per room night, high season; breakfast is included) is imho reasonable, and I can't really fault the hotel nor its staff who were really helpful from making enquiries via email before the trip, to helping us book taxis to the airport on the day of our departure.
Anyway, here's what you can expect if you stay here. Note that there are 2 establishments literally side by side; a boutique hotel & the B&B which is where we stayed.
Rooms are clean & spacious. There are anti-mosquito grilles in the windows (which can be opened, but there are no views to speak of). Toilets are equipped with WC & shower. Towels (rather threadbare) are provided. No AC outlet for electric shavers. No telephones in room. A TV with Thai channels, BBC, Sky News, Australian Network, German, French, Italian channels. Mini fridge with 2 bottles of mineral water free, topped up each day. Beds very comfy. No in room safe, but you can deposit your valuables with the front desk who will lock it away in the hotel safe for you.
There is a restaurant/cafe where breakfast is served from 0730 - 1000 every morning. You have a choice of 6 menus ranging from ham or sausage & eggs with toast, to cereals to pancakes to omelette with rice, Thai style. I don't think this menu changes. The cafe also serves lunch & dinner, but it's probably better to wander around; you'll be spoilt for choice.
Location wise, the B&B is in the heart of the old city, & right next to Wat Chedi Luang. Most of the attractions within the old city are within walking distance, including the Sunday night market which was literally on the hotel's doorstep! Despite its location, it's really quiet at night. Even the noise from the Sunday night market didn't travel to our rooms.
Staff speak reasonable English, are polite & helpful. Kudos to them, they really made the hotel seem warm & personable.