It was significantly faster on all platforms, plus looked good on all platforms. That also was a big deal on Linux, where things usually don`t look good.
I was on Firefox back then as well, and the only place Chrome(ium) ever seemed faster to me was initial startup - which was irrelevant because I always had the browser open in the background.
That was never my experience in practical, day to day usage. I feel like an odd man out though. I see many posters here talking about terrible performance on Mac. I've been running Firefox on MacBook Pros since 2007. I don't know what you guys are doing...but I can't replicate the poor performance.