I was just in Austin for 2 weeks, driving in Austin during rush hour is easy compared to Seattle, San Diego or LA. Whereas going 20 miles in Seattle might take me an hour and a half in Seattle at 5pm, that same trip from South Austin to North Austin is 40 minutes.
while I don't disagree that many cities have worse traffic, your vague example of "South Austin to North Austin" isn't very convincing. All I can say is that I live 12 miles north of my office downtown, and it routinely takes me an hour to get home.
Is there bike infrastructure? A healthy adult should be able to manage 14mph or so. 17 or 18 isn't crazy if you're in good shape (though stop lights kill this).
The bike infrastructure seems to only exist south of the river (what some would call "real" Austin). Outside downtown there isn't bike infrastructure, and it is dangerous to bike/walk as most streets are built 6 or more lanes wide, plus a freeway down the middle on some arterials.
Drivers do not expect people to be on foot or on bike, and the arterials are 50 to 60mph in North Austin. Considering that it has become moderately dense with Apartments & Condos in the past decade, its sad that it is dangerous to walk in that area.
To be fair, Round Rock is 20 miles away from downtown Austin. While growing up in Austin we didn't view Round Rock as a suburb, but as a completely separate city that happened to be fairly close by. It seems only normal that someone would want to work and live in the same city, and for that need not to be seen as a flaw in either one.
You are right that round Rock is not Austin. The point is that the radius from the city center that is acceptable to commute from is rapidly shrinking in austin. People are flocking here and the only option is to drive on mopac or 35.
Poor, good chunks of the city have no bus access, I ended up staying in an area that was pretty dense (3 stories minimum) and Google Maps said there was no possible route via mass transit. Turns out the bus is over an hours walk away.
there is one light rail line, and it runs like once every 30 mins. I can't speak for the bus system, since it doesn't make sense for me living in North Austin. It took me 15 mins to drive to the train station, 40 mins train ride into Austin, and then 15 min walk to my office downtown. The drive into town is half that if you come in early, so I opt to drive.
MARTA in Atlanta is pretty good from what I've seen. Rail has been on-time (+- 3 mins) every day since I started using it 6 months back. Service is decent, facilities are pretty clean imo, and the MARTA PD is always present.