Same here, you should add a poll option for 'I use both'. I use Firefox for surfing, and Opera for viewing sites with CSS
Firefox. I have tried opera when it first came up and it is very similar to firefox. But i've used firefox for so long now i don't think i'll change.
The only \difference between the two is that Opera can view the latest CSS and CSS2 standards, where FF doesnt..
The reason i like Opera so much is that i have the newest version without ads. With the ads i dont really like it at all.