I could not imagine visiting Yellowstone National Park and not taking the time to watch Old Faithful erupt. The National Park Service makes it very easy for you: tons of parking, lodging and restaurants within walking distance, schedules posted to help you time your visit, and even benches to sit on while you wait for the show.
Tammy and I planned our trip to Old Faithful so that we would see its eruption in the morning, hopefully early enough to miss the crowds, and then begin walking through the adjacent Upper Geyser Basin in order to see many of the other geothermal features that are neighbors to Old Faithful. Our planning worked out quite nicely, and we also got lucky. We got there early enough to beat the crowds (later in the day, it was very crowded), and managed, quite by accident, to walk up to the geyser viewing area about 10 minutes prior to its eruption.
Here is my proof that I was a good Yellowstone tourist and I took the time to watch Old Faithful erupt.