Thanks for the tip, Doctorow!
I gave it a quick try and it looks neat. You get an interactive slider bar that controls the degree of personalization (Min to Max). And when it's a personalized result it has a little icon next to it. You can see those items slide around in the result order based on how much personalization you choose. Really looks cool!
In fact, I've set it to be my default homepage (instead of the main Google page that I used to have). Only wish it would personalize news search results also. I sent feedback suggesting that... maybe that's part of their plan over time, anyway?
And noticing the url, I also tried
http://labs.google.com/ which was new to me, and very interesting. Google really seems to have their act together, and they're not resting on their laurels. They're taking very creative and logical steps to do things right, and it shows in their results!
This one belongs on the front page...!