I haven't been everywhere in the United States yet but I've been to a great portion of it between leisure and business travel. There really is a lot to see. I generally consider the landscapes of the west the best thing this country has to offer with the Grand Canyon being my top recommendation to travellers.
My Personal Experience:
Overall Impressions: Austin was generally laid-back (unless you are talking football). The city motto is "Keep Austin Weird" - a slogan you'll find on the standard assortment of souvenirs. There was a mix of college town and mid-sized city atmosphere at least downtown where I spent the majority of my time.
When I Went: February 2007
Purpose of Trip: My goal was to get a small taste of Texas while experiencing the music scene / nightlife that Austin is known for. I was told Austin was a better representation of Texas than San Antonio by someone along the way. My original plan had been to visit both over the course of a 3-day weekend, but a series of airline snafus led to staying in Austin the entire trip.
Primanti Brothers sandwiches - a local chain with grilled sandwiches served with cole slaw and fries stacked on the sandwich themselves.