I was sent to Vienna for work in the early 90s...and never really went back to the US (long story). I love it here after 30 years for the same reasons you loved it after a week. Someday when I retire I'll have time to write about it. For now...just comments:

Käsekrainer: Your picture is a perfect example except most people eat it with mustard. When ordering in Viennese slang, you want "An eitrige mit einem Buckel" which literally means "a pus-y one with a hunchback" the "pus" being the gooey cheesey goodness, and "the hunchback" being the butt end of the breadloaf.

U-Bahn is short for Untergrundbahn which is (not surprisingly) "unterground train." The yearly cards are even cheaper, at €34 / month. For a long time the city kept the price at €1 /day. Public transport is subsidized as it is much cheaper than road and emission repairs, not to mention traffic issues. 60% of Viennese use public transport at least once per week.

Vienna is one of the (if not the) greenest European capitals. If you go back, I recommend The (green) Prater (not the part with the amusement park, although that is fun, too). Der grünen Prater was the private hunting ground of the emperor. It is still quite wild. If you get out early in the morning you'll see deer, hares, sometimes foxes, badgers, hedgehogs, and rarely a wild boar (only at the far end from the city). We walk our dog there a lot. It is like being in the woods in the middle of city. Prater is larger than Central Park IIRC.

Even after 30 years I still am stunned by the beauty of the architecture. I hope I never lose that feeling of wonder.

I could go on for hours, but I'll close with saying that Vienna is affordable specifically because the socialist city government has made affordability a priority for 100 years.