If you're coming to Taipei then you should definitely include this place in your list because it has one of the best spots to get a clear view of Taipei101. Hands down, it's our favorite place to take a great picture.
All you need to do is go to Google Maps and search Takemura Izakaya; that's the exact spot for this photo! Do note that it's quite a small alley, so there might be people already there taking pictures! But usually it's fast.