Great value - in general, Turkey is a very affordable destination but this hotel was by far one of the best bangs for our buck. We booked the Imperator room (#407 - which is on the top floor) and we were not disappointed. Very spacious with lots of cupboard space and room to move around - it felt truly luxurious after spending 4 days in a shoe box in London, England. The hotel is a small boutique one - still feels new and is kept very clean. The free WiFi was reliable, which always helps if you find yourself needing to do a bit of work while on vacation.
Selchuk, at the front desk, was very helpful with restaurant and entertainment recommendations. (BTW, if you are from Canada, he is a fan of Leonard Cohen.) He was readily available to assist with directions and setting up transportation to/from the airport (50 euros, roundtrip). We would recommend this as the taxi drivers in Istanbul are supposedly notorious for ripping off foreign tourists. (Tip according to Selchuk for taxis if you want to take one - look for an official "station logo"...it's painted on the side door of the cab, along with the car number.) We avoided taking cabs and instead opted to walk and/or take the tram (the latter option being very economical - about 3 lira for a one way trip...the Sultanahmet stop is about 5 mins from the hotel and there is a kiosk to buy tokens there. They gave us a tramway map at the front desk - the tram is modern, clean and very easy to use...stops are announced in advance and there are multiple lines servicing different districts.)
As for the hotel environs, it's a bustling area with many other hotels and restaurants. There are a number of mini-marts on the street where you can buy bottled water and other groceries. It is a vibrant area so it's not whisper quiet but we had no issues with street noise. We couldn't have picked a better area to stay in for our first trip to Istanbul. There are so many exotic sights and sounds - it was all so wondrous.
In case you are wondering, this hotel (and the general Sultanahmet area) is a world away from the unrest that transpired in Taksim Square - it wasn't an issue during our trip. (Note, you can also take the tram to the European part of Istanbul.)
As mentioned by other reviewers, the Senatus is in an ideal location with the Hagia Sophia, Blue Mosque, Topkapi Palace, Basilica Cistern, etc. no more than a 10 min walk from the hotel. We must have passed the Blue Mosque at least a half dozen times during our 4 day stay at the hotel - a breathtaking sight in the evening. (For attractions, we noticed that they have one day, or two days in the case of Dolmabahce palace, that they are closed. Also, note that there is something called a Museum Pass that gets you access to a bunch of places - had we known about this, we definitely would have bought it as it nets out to the same if you visit 2-3 places AND you avoid what can be very long lines! There seem to be two options, with the more expensive one giving you admission to more places - do some research and save yourself from having to wait in line ups.)
The Grand Bazaar and Spice Market (Egyptian Bazaar) are also within walking distance from the hotel (about 25 mins and 40 mins, respectively, at a moderate pace).
The one thing about Sultanahmet is that people are relentless at attempting to get you into their restaurant or store, buy their wares, or join their tours (as they accost you on the street). Be polite and decline - but be prepared to be cajoled, implored, mercilessly entreated...you get the idea.
Finally - the BEST Turkish delight can be found at Cigdem (on the main road, Divan Yolu, near the Starbucks). A local recommended this place to me as the place where she buys from when bringing gifts. We're savouring the last of the most awesome delight we've ever tasted and are wishing we had more!!!