The layout looks more AJAX-y; lots of simple rollover effects, seems a little more responsive.
Web-based Marketplace is still down.
I can't find how to compare games with Friends anymore. It used to be Friends > profile > More Games > select the title, and it would give a comparative layout. "More Games" isn't there anymore. (reads official xbox.com forum) Oh, it's in the per-user popup from your Friends page now. That's... arguably more convenient, provided you know to hover to bring up additional information.
Unlike NXE, it's probably better than before overall, but it's going to take some getting used to.