Good - Friendly, really kind and generous people generally, good food, great wine, interesting culture, lots of places to explore, "outward looking" mentality of the Portuguese, fun cities, lots of outdoor sports hobbies/activities you can do, good affordable public transport most areas, good sense of community and social solidarity, festivals and regional celebrations, more holidays than the UK, established ex-pat communities most places, easy to get by in English, healthy, easy to get work teaching English, quality of life overall, lots of passionate hard-working educated people, most things are easier than they used to be.
Bad - Low wages, high taxes, poverty, Lisbon-centric, mass tourism and its impact, a degree of resentment against tourists/foreigners, quite a homogeneous culture, outside of Lisbon you will probably get bored culturally/musically/socially compared to the UK, everyone smokes, fairly shit healthcare system compared to UK/Spain, often expensive - cars, technology, imported goods etc, bureaucracy (like Spain, no one knows the answer or there are several answers or there is some reason why something simple can't be done), can be cold and miserable in winter, very hot in summer, very limited job opportunities outside Porto & Lisbon, the Portuguese can be miserable fuckers, legacy of racist and imperialist colonial history, hard to learn Portuguese unless you're motivated but it's important to do so for important things and you really should.
I've traveled in Portugal a lot and have a fair few friends living there, so that's my take on it. I can get by in Portuguese and that opens many doors. If you can work remotely and earn like 2000 quid or more a month you are set and will really have a great time living there, but don't rush into buying property or committing yourself, take it slowly. It's like everywhere - some of the frustrating things are also some of the best elements.