* Cost of living for a good quality of life still being relatively high or rising, especially in Lisbon and other tourist/expat areas. And a second tier city in Portugal is much less of a clear choice since that is comparable to a lot more places.
* The tax system being very complicated. One can always argue about how much tax to pay, but few people want a complicated tax system, especially not as a foreigner. (And is usually an indication that other systems are complicated as well).
* The tech scene not really happening. Despite the usual "next Silicon Valley" it doesn't really stand out from anywhere else as far as I can tell.
There might certainly be things I don't see, but at least initially it doesn't seem like Portugal rise above the competition to the extent that you wouldn't have to consider quite a few other options.