There are lots of places that are nice to visit, but which don't necessarily have long term appeal. I generally prefer traveling to places I could imagine spending a few months in, even if I only have a few days. One doesn't always know which is which beforehand, of course. I was in Lisbon a few years ago and would definitely put it high on the list of "great places to hang out in." Also, too, Portugal isn't doing so well economically at the moment so they could probably use your tourist dollars. It's pretty easy/cheap to travel around the country by train, too, so one doesn't have to limit oneself to Lisbon. I hate Frank Bruni, but this was pretty decent.