>The money from ZIRP mostly goes to the upper class as it props up asset values - stocks, land & housing, luxury goods, etc.
One that people tend to miss: compensation for high-income professionals. When that gets bid up, so does the price of everything they spend money on. Education/childcare, personal electronics, healthcare, transportation, food, etc. It's not just the wealthy and ultra-wealthy; when the upper middle class can pay and not feel pain, that's taken as a signal to jack up prices across the board.
I would most certainly categorize what is commonly known as the "upper middle class" as wealthy. Upper-middle usually has a sizable wealth, mainly in real estate, equities, etc.
So it is not only the rich and ultra-rich (but of course them benefit from this the most if they don't do anything too stupid).
Of course all of these terms and definitions are quite fuzzy so the whole argument hinges on some implicit agreement as to the specifics.