I started using chrome when a few sites I go to would not work on ie8. But then chrome doesn't let me directly control security and cache behavior like ie does, so I have doubts about security. I went to my bank web site once, and didn't tell chrome to store the username/passsword, and the next time I went to the bank site chrome had not only cached several https pages with account info, it also stored the username password.
So I use chrome for most general web use but for online banking and other stuff where security is important (AND I have some trust in the company running the website), I use ie, because I can tell ie to flush the cache on shutdown, can tell ie to never cache secure pages, and ie hasn't stored all of my account login info for pre-fill typeahead "assistance". Chrome let me down hugely the one time I used it for bank access, so I don't use it for anything important anymore.
I haven't tried ie9 but as usual I'll probably simply decline to "upgrade" ie for a while until the bugs are worked out or until it becomes the default browser for new installs.