Great location, close to many attractions. but off the beaten (and noisy) paths. I particularly recommend walking down to the wonderful café district behind the Kılıç Ali Paşa Medresesi in Karaköy for breakfast.
The place is simple, but comfortable and well-furnished, with everything you might reasonably want (except maybe kitchen, but you don't come to Beyoğlu to cook at home; and TV, but who needs TV these days?). It was also spotlessly clean. More space and more comfort than you get in most hotels for comparable price. But keep in mind that there's no elevator if you have any mobility issues.
Cüneyt was very helpful and attentive, answering all my messages practically in an instant. High recommendations.