I've had Artu for lunch. Very good simple Italian, reasonably priced.
I've had Rabia's many times. I tend to think they used to be a lot better, but I'd still go again.
Outside the North End, I've had Via Matta (Fantastic). Although not Italian, more Mediterranean generally I'd recommend Avila.
Now, I work in the North End...but it would get expensive to sample all these restaurants, so I'm wondering about any other recommendatoins, whether 'simple' or fancy....