Is that 9% of the 43% as in if you had 100 users, that's 9 users or if you had 100 users that'd be ~4 users?
Once any browser hits single digit percentages, I typically don't fully support them if they are an older version. E.g. once IE7 hits below 10%, I'm done with it. I'll make sure it isn't completely broken, but minor issues will be ignored.
While the compatibility mode does render it as IE7/8, it's not foolproof. There are still quirks unfortunately. But yes, do try out the different services out there.
While I cannot given out specifics... let me put it this way. We have a target audience that is different than most sites (those that know computers better.) Chrome + Firefox combined are roughly 80% of our traffic. You can see that varies greatly from what floridaflatlander was seeing
As a web analytics developer, I can tell you no site will be the same. If you have an existing site, make sure you have analytics on it and use your own data. If you don't have a site up yet, know your target audience. Is it going to be older people who may not know computers? Or will it be college kids who might know a little more?