My current car (2005 Pontiac Bonneville GXP) and prior car (1999 Bonneville SSE) both have/had HUDs - Love 'em. My mom's 2011 Camaro also has a HUD. Speed (and engine RPM in the Camaro) are shown constantly. High beam and turn indicators illuminated when active. A "Check gauges" Warning when idiot light on or gauge amiss. The two newer cars also show limited radio/song information but only when user is changing settings.
These aren't the kinds of things people are complaining about. There is no difference (IMHO) between a speedo on the dash and a speedo projected on the windscreen. I drove a 2013 Camaro (rental car, so no fancy projectors for me) and I liked the digital speedo readout between the dials (especially since the steering wheel blocked half the dial, but that's GM's design team for ya). But in the end, its the same device with the same function, just different ways of displaying it (I do agree with you BTW, HUDs are awesome).
What people are complaining about are things that detract from common sense. Blindspot sensors coddle incompetent drivers into not checking their blind sport (and subsequently crashing into you because the warning buzzer was ignored), lane assist, brake assist all make drivers lazier and more complacent. These kinds of warning buzzers are what they are talking about, it becomes more important for an incompetent driver to find out why their car is beeping than actually watching the road and there are buzzers for a lot of things, seatbelt warnings, lane warnings, distance warnings, cup holder open warnings, perceived fatigue warnings... each one has a buzzer that drives the driver to distraction.
Its the same with reversing cameras, there was a camera on that Camaro I hired. It was nice but didn't stop me from doing a head check because people and cars come from the side as well as directly behind me. However I'm the exception here, I see more and more drivers with their eyes glued to the screen in the console as they back out completely ignoring the objects not directly behind them... The last one who did this to me as I was walking through a car park received my boot to rear quarter panel (and looked at me as if to say "what was that for") and that was last Thursday.
We now have smart cars and dumb drivers.