I left Madrid to work abroad a few years ago. I visit the city often, that is more than four times every year.
I find that Madrid is changing rapidly. For instance, foreign immigrants used to be rarely seen in my teenage years apart from the pioneering Chinese; now Sudamericanos, Romanians and Polish seem to be everywhere. That is particularly noticeable in the public transport, where, in many cases, immigrants clearly outnumber native-looking people.
The Metro (Madrid underground) is extended and now it is probably the cheapest and best that I never seen anywhere, and that includes a few American and European countries.