Wow, that is unusual and terrible lag! The Tab 8.9 is a pretty fast tablet and it shouldn't lag like that. I'm assuming you've rebooted it and emptied your browser's cache? I can't say ICS will fix this because it shouldn't be lagging serious with Honeycomb.
Samsung is typically slow with major version OS updates. With ICS, it seems many manufacturers are taking quite some time to get updates out, but Samsung is rarely among the first.
-------------------- Lisa Gade Editor in Chief, MobileTechReview