I've started flying into IAH rather than AUS recently and there are pros and cons. I find it relatively swift going through immigration at IAH, so it's never a long wait (and even quicker if you have Global Entry), but the big issue with IAH at the moment is all the construction work, making the airport a mess and hard to navigate when it's your first time.

The good news is though, there's an underground (tiny) train that connects you between terminals - I once parked in C and took it across to D for example. It's not the fastest train in the world and, frankly, a little claustrophobic, but it's fine, does its job and won't take more than 15-20 mins between the terminals.