Here's a photo I took of it from the roof of the Old Faithful Inn:
Since I worked out there for a number of years, I saw it erupt many times. You almost get immune to it. Almost. But it still was always impressive.
The pic above was taken in May, when there are still not many tourists in Yellowstone. At the peak of the season, in June, July and August, that boardwalk is packed. For two of my seasons out there, I worked in the building visible in the background of the picture. While people waited for the geyser to blow, it would be slow inside the building, but after it erupted, there would be the inevitable "geyser rush" and we'd be swamped.
If you want to see the geyser live via webcam, go here.
There are bigger, more impressive geysers out there, but you often have to walk a bit farther, or wait longer - sometimes a LOT longer. Despite the geyser's name, it's not totally faithful. Lots of the tourists assumed it went off every hour on the hour, or something like that, which ain't the case. (Tourists have a lot of strange misconceptions about many things in the park. Some of them provide fun fodder for the employees.) If you do get out that way to see it, it's cool to go out and watch for it to erupt after dark. You hear it more than see it, and what you do see is this ghostly mist rising silver against the stars. Very cool!