My wife and I stayed here for the first leg of our honeymoon and had a really nice stay. The location is great and is within walking distance of Christ Church and St Patrick's Cathedral. You can also walk to Guinness, Teeling and Temple Bar if you're okay with walking for 20-30 minutes (worth it in my opinion).
Gonzague was very accommodating to us in helping us get checked in. We had a big travel issue when our flights got moved around due to weather.
We had a few issues, but most are out of Gonzague's control. The gate closest to the building needs to be repaired as you really have to fight it the automatic opening process. The gate further left worked fine though. The hot water went out with two days left in our trip. We didn't use much as we were only in the flat when we were sleeping or showering, not sure what happened.
All of this being said, I would gladly stay here again.