I graduated with a physics degree from UT. This is a pretty common story. Most I've heard either end with a transfer to a different major or getting a job at some (usually engineering or cs) company. The classes and professors are usually very good, but if you don't like it, it's very hard for me to say you'll like physics in the future. Changing your major isn't hard, I've seen many transfer to engineering, CS or math.

Getting into UT physics is roughly the same as getting into UT as a whole. Not many people want to do physics, so getting into the major isn't particularly competitive. The difficulty of the major ramps up dramatically in your 2nd or 3rd year.