I'm gonna crib a portion this review from my larger analysis of the Banrai Hotel itself, which contains this izakaya, and is run by the same people (it should be noted that the izakaya bar also doubles as the check-in desk for the attached hotel above).
Izakaya Banraisyuten is...well, it's not terrible. It's just not great. The steak we had on our first night there was a little fatty and gristly, and definitely our least favorite gyuniku dish we had during the entirety of our trip; the peperoncino pasta was similarly OK, but not particularly inspired. Drinks seemed a little overpriced, and unlike other bars/restaurants in Tokyo, this izakaya is owned by a Japanese ex-pat and a Canadian, so tipping is somewhat expected here, making the whole experience seem a little...off, from what you'll experience elsewhere in the city.
Service was a little weird as well, at least during our first night: it was hard to get a straight answer about the availability of certain items on the menu at the time (it was later at night), as well as specific details about certain entrées. We managed to figure it out, but it was strange encounter, to be sure. We would visit a couple more times during our four-day stay, but only for drinks, as we hadn't been particularly impressed the first time around.
Still, the atmosphere is lively, and we met some interesting characters here, including a report for the New York Times, so we definitely have some fond memories of this place. I'd say they need to tighten the screws on their service a bit, and maybe make some minor tweaks to the menu, and they'll really have a fantastic establishment on their hands here. As it stands, the only real reason to drink or dine here over anywhere else in the immediate area, at the moment, is if you are a customer of the hotel, and aren't wanting to venture out into the city, which, if you ask me, defeats the point of being in Tokyo in the first place.