Take Apple for instance. They take something good from something and then put it into their something. (???)
Their new beta version of Safari 4 is really pretty and very fast. It takes the pretty features of Google Chrome such as the title bar tabs. They then takes features from their iTunes, which took features from someone else, such as coverflow and made it look really pretty.
Where as Firefox 3.1 beta 3 has great techy features, such as the new TraceMonkey JavaScript engine, Web worker thread support, Native JSON support and improved Gecko layout engine.....
It still reigns supreme. It's Add-ons are forever the reason. There is going be one add-on that is indispensable to someone. That's if they know that they exist.