I've had IE9 running for a few weeks now. I LIKE IT
They did change up where you find certain tools, but overall, 2 thumbs up. Its much faster (perceptively) and uses less resources (Your results may vary, ya-da, ya-da, ya-da)
The ony issue I haven't been able to solve, is an issue on the coal forum.... The "Take me to first Un-Read Post" button does not work correctly. I've been using the "Take me to The Last Post" button to get around the issue.
On the security software, I removed AVG long ago, and am using the free "Microsoft Security Essientials". It does a better job than AVG, and uses a heck of a lot less resources than Norton.