The house is a nice one. It needs some small upgrades/fixes (ie: no mosquito nets on some of the windows, the gas stove didn't worked but was fixed the same day) but overall it's a spacious and comfortable house.
If you plan to stay only in Mellieħa during your stay, it's a great choice.
However is the plan is to see the rest of the island, expect to make up to 45 minutes and pay 30-45 EUR one each taxi/bolt ride (one way). So if you plan to visit Mdina/Valetta/Marsaxlokk/Sliema expect to spend up to 1.5 hours in taxi for each.
This is our second trip to Malta. Last time we stayed in Valetta and it was a much better choice given proximity to all points of interest.