The browser
I’ve always been on the Bêta version of Google Chrome. And the current bêta (soon to be stable I guess) now supports plugins, the most interesting ones are AdThwart which blocks ads and Gmail Checker which displays the number of received mails.
Making some chrome extensions seems to be really easy, it’s entirely based on javascript.
The other very interesting thing is the developper tools. They are very close to Firebug, it’s now really easy to debug JS and CSS within Chrome.
The browser also bookmarks synchronizing using the google account. But I’m not sure everybody will love this (big brother blah blah blah).
The OS
It surely starts fast but as, in this beta version, it’s just a browser it’s not really interesting. I hope they will add a lot of stuff around it.