This doesn't surprise me too much. When you think about it, most of the people downloading FireFox are probably early adopters who are considered very tech savvy. The typical IE user could be anybody who has bought a PC since 1998 - a wide demographic.
However, I have noticed that my banner CTR across both platforms is considerably less than text ads. I have observed this trend for over a year.
That's very true. Think about it, when you first start off with the net, you go with a portal ISP like AOL because you don't know any better. Then, as your knowledge of the internet and ISPs grow, you realize AOL blows, so you drop them and go to a straight ISP. The same with web browsers. You use IE when you first start out, which means you don't know all that much, so you're liable to get fooled by all manner of ads (all those "you've won!" or "click here to win!" ads) but after you've been surfing for a while, you just ignore them. Likewise, when you've been doing this for a while, you realize the limitations and dangers of IE, so you jump to something else like Firefox. I'm using Firefox to post this message right now!
Amen. I have to say that I personally *HATE* any type of pop-ups or pop-unders. Can't stand them. Which is why I'm also posting this message right now from FireFox. Haven't seen a pop-up in more than a year.