Google this afternoon announced that it has finished the latest upgrade to its search engine, dubbed "Caffeine," promising "50 percent fresher results for web searches than our last index." In essence, the system incorporates web pages into Google's index -- the thing you're actually searching when you do a search -- more quickly after they're crawled.

Check out the Google Blog for all the gory technical details, but to help people conceptualize the change, Google software engineer Matt Cutts gave a great analogy this evening at the SMX Advanced event in Seattle -- comparing the delay between crawling and indexing to the typical wait for different forms of transportation.

"Your documents used to be on a bus. Now they get to be in a taxi or a limo," he said. The upgrade, he said, "essentially makes the entire index closer to real time."

Cutts made the remarks at the outset of a lively keynote discussion with conference organizer Danny Sullivan of Search Engine Land. Among other topics, Sullivan teased Cutts about Google's new three-pane design, which includes related links and search tools in the left-hand sidebar, similar to Microsoft Bing.

Sullivan called the design that "thing that you stole from Bing that Bing stole from Ask."

Teasing aside, Cutts said the response from users to Google's recent design changes has been good, based on testing and usage patterns so far. Sullivan asked for a show of hands, and from my vantage point, the crowd seemed divided pretty evenly among people who like the new design, people who hate it, and people who don't care.

Cutts followed up by querying the search-savvy crowd about browser usage, and the overwhelming majority were Firefox users, followed by Chrome, with Internet Explorer coming in a distant third.

And one last note, although this is slightly off-topic: Cutts offered a defense of the Google Buzz social-networking system, saying he has warmed to it as something that fills a need in between tweeting abd blogging -- allowing him to post more than 140 characters but less than a full-fledged blog post. He encouraged people not to dismiss it.

People in the crowd didn't seem very convinced.

See the SMX conference live blog for more on the Q&A with Cutts.

SMX Advanced Seattle continues on Wednesday morning with a keynote Q&A with Microsoft Bing VP Yusuf Mehdi. Check back for more coverage on TechFlash in the morning.