Mafalda's flat was lovely and in a great location. It's pretty easy to get anywhere from the steps up or down (tip: use the train station escalator if you don't want to come up the stairs from Rossio square). A grocery is close by, too.
The bed was comfy and the shower had good pressure. Windows did a good job of keeping out noise.
a couple things to note: there's no salt/pepper/oil, but we also encountered that in other places. Also the front door is a little tricky to open but once you get the hang of it, it'll be no problem.
If you're thinking about booking, just do it!