I've just done two (unsuccessful) rounds at IVI Lisboa. The good - it's the most well known clinic in the country and uses all the same methods and equipment as they do in Spain. It's slightly cheaper than Spain/UK.
The bad - it's like a factory, there is no personal attention and the doctors are overworked, tired and rushed and there are far too many patients. You often get shunted from one doc to another - I didn't feel that anyone cared about whether things were a success or not. Many of the nurses don't speak good English and some don't speak any English at all. No one tried to make me feel cared for, no one explained things properly or in depth, many of my questions and concerns were dismissed. I was just expected to follow the treatment without questioning or understanding. I thought it was because they were speaking English but my Portuguese husband said he felt the same when talking with them in Portuguese.
I don't know whether my treatment there was unsuccessful because they dropped the ball in the lab (I'm 44 so my odds are obviously crap, but I got 19 eggs so at least a couple should have been OK...that's another story).
As I understand it there is a long waiting list for egg donors.
That said, I don't know if any of the other clinics would be better. Portugal is really a third world country in many respects and while the technology and education they have is first world, attitudes to patient care, bureaucracy and customer service is still very much stuck in the past.
Let me know if you need more info!