I tought i didn't need a software like that, but because Google decided to buy it and to give it away for free I was too curious...
And I found it's much more usefull and well done than I expected!
The interface is really great, the search funcion is fast and it can even export your albums to the web (altough I'd really like to have a plugin system so that I could export the metadata to my website's xml format)
So now go and try it yourself http://www.picasa.com/google/?