How important is it to have a workout buddy?

Helpful. I think the benefit of a workout buddy is that it will keep you honest. Harder to skip a workout when there is someone else relying on you to show up.
More success. Several benefits to a workout buddy: 1) more fun - can socialize while exercising, 2) won't get bored, 3) if you're competitive, you might end up competing against each other (within reason), 4) will push each other to workout on days when one of you doesn't want to. 5) will coach each other even outside the gym or park. Workout buddies aren't essential to fitness but improve the experience.