It looks like they've sped up forward/back, folded in some of the extension features and fixed the awful autoupdate. The coolest new thing to me is the newfangled SVG/Canvascape support. Here's a couple of neat demos.
http://www.abrahamjoffe.com.au/ben/canvascape/
http://www.croczilla.com/svg/samples/svgtetris/svgtetris.svg
Yay, no more Flash!
Well... for Firefox users anyway. I hope this makes for some cool Google Maps mash-ups.