For the longest time I was a devout Firefox follower and carried the anti-IE banner. Now that I exploring a career in web development, I realize I will need to use IE along with other browsers (Seamonkey, Safari, Opera, etc) to check my work, and I will have to be proficient in their use. Basically I have to become browser-agnostic.
Most browsers have similar behavior, and from the user's point of view are not all that different. But they do have their quirks, and I will need to learn my way around them. I just have to make sure that my geekitis doesn't flair up, and I spend too much time playing with the new toys.
(One little side note: I originally composed this entry on Seamonkey, and I noticed that the fonts and size were different than entries I created on Firefox. I believe I need to set the font and size in Seamonkey, but this is a good example of why you need to be browser-agnostic and learn the differences between your tools)