I paid for Opera (twice) because it was clearly the superior product. People spend money on a better machine, so why not on a clearly better browser? (At that time).
And although browsers are no longer distinctly better than each other, I still donate to Mozilla.
Not really, I was an Opera user when Firefox 0.8 came out... Switched pretty much permanently, Opera also had mouse gestures which I was actively using and still use with a Firefox extension...