Excellent stay: This apartment in Entrecampos right in front of the University was a pleasant experience. It was in a great building, clean, had everything you could need in a flat + plenty of closet space, two VERY COMFORTABLE, NICE single beds for you and a friend (or can be put together for two), washing machine, couch, etc etc. Only complaint was low shower pressure, but everything else made up for it. Thumbs up overall!
Location, the good and the bad: It's a bit off from the city center where you'd want to eat, walk around, and sightsee -- you have to take out about 30 min to take the metro/bus. However, Uber/Uber pool is relatively cheap and if you have more than one person to split the bill, being a little ways off is no problem.. and you get to stay in a peaceful neighborhood/nice spacious apartment! There are many cafes and maybe a restaurant or two right on the ground floor (but most are closed on Sat/Sun). It depends on your preference for center of the city vs. being away from the chaos when going "home" :)
Close to airport: A head's up that this place is a 9 min drive from Lisboa Airport (great for landing/leaving), but that means the planes fly very low when you're in the apartment and you will hear them out the window frequently. It wasn't a problem for my friend and me, because we can sleep through any noise. There are probably other noises if you stay closer to the centre, but if airplanes landing isn't your thing...
We had a great stay and appreciated going back to a nice cozy home at the end of the day. Especially because this place has BLACK-OUT blinds that assist shut-eye time, and great door-windows you can open in the morning to breathe in some fresh air on the balcony :D Thank you, Tipuana!