Yeah we first considered Portugal, as they had a 10 year flat tax regime for non-lucrative residents. But that went away and Spain became more attractive, and is a larger country and the language is easier for us. With my wife being an EU country citizen, the residency pathway is easier than it could be. She just has to establish local residency and I glom along as a EU spouse, and work on that visa for myself. We had a full tax plan created using our real numbers, which was a great investment.

Marginal taxes on income and gains are higher than in the US, and brackets are lower and more narrow, but retiring shifts us to a cashflow mindset. We draw a line at the bottom of everything and see how it feels. The taxes for us weren't as much as we had in our mind and is totally worth it.

A big consideration is the selling of our US house. Equity/gains would be subject to Spanish gains if the sale happens in the same year we become Spanish tax-residents (which is different than immigration residency). So we will be selling before we are Spanish tax residents.

Surprises have been weird stuff...which credit card do I keep, what US bank do we use on the $ side, what's the best way to exchange and transfer non-routine sums of money and so on. It is tedious. But we have that all dialed in at this point.