I'm one of those lurkers who doesn't want to follow a group day by day, but is interested in searching a particular group for discussions about a particular topic occasionally. As far as I'm concerned, Google's takeover of Deja's groups is the best thing to happen to Usenet... ever.
Previously, if you wanted to search Deja for information on anything, you had to go through a godawful interface, plastered with ads, which didn't even work half the time. Now searches are incredibly fast and the interface is clean and intuitive. I know that people want threaded views, storing of favourite groups, etc. - but based on past performance, the odds are that Google will deliver these enhancements any time soon.
As for the criticism that the archival of public newsgroups should be a public service, I can see the point - but I also believe that a big company like Google is far more competent to deal with the service. Ideally, Google should make a pledge that if they go under, the archive should be released to the public for free.
In summary... Google, more than any other site, has improved my web browsing experience. Now it looks like they're going to do the same for Usenet.