My girlfriend and I stayed at Isabel's apartment in early July 2017 and we had a really fabulous stay.
The apartment was very clean and had everything we needed, including a very comfortable bed and a well stocked kitchen. There is comfortable enough space to have a meal or two at home if you fancy cooking and saving a bit of money. From the balcony (not big enough to sit) you can see the local church and the river. The apartment is accessed by two narrow flights of stairs - there is no lift, in case that is an issue.
The best thing about the apartment is the location. I don't think we would have chosen better. It's right near the river (north side) and some beautiful cafes and restaurants, but not noisy.
Porto itself was awesome, with loads to explore and great if you like to drink port! Food was good everywhere we went, in particular a restaurant called Bacalhau, which was stunning, and only five mins walk from the apartment.
Isabel was warm and welcoming and we always felt we could ask her if we needed anything.