The view is utterly amazing! Totally worth the money! You really get a sense of the way the city goes up and down far out into the distance.
Inside, the place also looks good and is a very decent size for Lisbon, and the building itself is very beautiful on the outside. But bear in mind it is an old building, and the stairs inside leading up to the apartment aren't that awesome to look at (or walk on).
It is pretty easy to get from the Martim Moniz metro station/square (an area which is really lively in the evening - with dancing and food stands; the back streets may look a bit unsafe - although we had no issues whatsoever).
All in all, this place is truly great!