Apparently not a lot, interface-wise. Most of the changes in this version are under the hood, covering standards support, from the “resolution” media query and the <datalist> element to Shadow DOM and MathML, and new extensions APIs, for example for capturing the contents of a tab.
If you’re interested in the performance of the browser, Chrome has a built-in about-page for visualizing it, chrome://performance/ – similar to telemetry in Firefox. You also need to turn on the flag called ‘Enable performance monitoring’ for the data to be gathered as you use the browser. This page has been redesigned in version 24 with a style more inline with the other setting pages in Chrome. It features three controls on the left for the time range (hourly, daily, weekly, etc.), type of metric to display (CPU usage, memory, network load and time to load page or to startup the browser) and the events (software updates, crashes and freezes or extension installs/uninstalls) and on the right four graphs based on the four metrics. Unfortunately I don’t see a way to export this data in order to analyze it and some useful information (like the number of tabs opened at that time) is still missing.
Other small changes include a new flag enabling password generation for account creation pages in the browser. I didn’t see this in action yet, as I’m using LastPass for that. And at some point, the RSS feed viewer introduced in version 21 and still present as of today in the stable channel has been removed, and Chrome only shows the bare XML version of the feed – another reason to keep using bookmarklets.