I'll add a couple of items here that might be helpful to some:
If you are departing northbound on the #22 at the Austin station and get the notification that the TE is going to be much later than expected and the vending machine isn't very appealing- you do have options nearby to grab a bite. There's an airstream trailer with coffee and crepes in the parking lot of the YMCA that's a quick 5 minute walk away. There's also a Whole Foods (has a good hot breakfast bar and tacos) and Starbucks in walking distance. I know for sleeping car passengers, Austin is usually last call for breakfast- but if it is late, you won't be eating until lunch.
If you are arriving southbound on the #21 and are a YMCA member, you have AWAY (Always Welcome At the Y) privileges, which allow you to use their facilities. Actually, even if you're not a member, you can get a guest pass at the front desk with a valid photo ID. The Townlake branch is next door to the AUS station. This is handy if you need to take a shower after a long ride in coach or you need to move your legs a bit. They also have a hot tub and steam room in case you just want to relax, too.