All you'll see in the program's main window are the days, hours, minutes, seconds and milliseconds running. That's it. You won't be able to minimize the app or stop it (an option that's only available in the full version).
Stop Watch is quite limited in its features. It's very simple, and this is of course a point in its favor, but something as basic as stopping the timer when you want instead of having to close the program would be nice.
In the trial version you can't stop the stopwatch.