Yes, it's very common in enterprise scenarios and with regular SMBs.

When was the last time you were in the office of a medium or large company that did NOT have an AD domain?

I'd probably guess its the most popular enterprise os excluding web hosting.

On average I've seen better windows server setups then Linux setups simply because windows servers tend be used in 'enterprise' solutions.

Absolutely, it still brings in billions in revenue each quarter.