I'm going to start by saying that this is one of my favorite B&B stays, and this is now my go-to place in Porto.
I have heard that the place has gotten a bad rap because the city is living and breathing around the place. To me, that's the charm of being in the middle of a real neighborhood with real people. If you don't like the smells of the local restaurants, or the sounds of a working class street, go stay in a hermetically sealed Hilton.
Downstairs is a fabulous sushi restaurant (and no, it's not your everyday sushi place, it's adventurous). There's also the best burger place in the city, called "Holy". At the top of the street is a great wine bar where the bartender really knows his wine.
The B&B room I had overlooked the street on the first floor. I loved the charm of the room, the bathroom was great, and having a small fridge and microwave is a great addition.
I'm not one for a firm mattress, so I can't praise that, but it was fine. I'd sleep on cotton candy if I had my choice.
One word of caution, and this is not the B&B's problem, there is a five-star hotel's spa and pool going in across the street. I arrived Friday evening and left early on Monday, just as jackhammers started. Not sure how long that will continue, but if you're a night owl and like to sleep late, be aware. I stayed mid-October, and I'm guessing this loud work will only last a couple of weeks.