Google launched an experimental application that can basically be used in as a replacement for Spotlight. Is it better? Well, it does seem speedier to me, but it's not a huge improvement in that sense -- the improvement comes in the quality of search results. Spotlight results do show up in the Quick Search Box results if you want them too, also -- that should make people a bit less nervous about trying to use this exclusively.
Currently, it doesn't search your Gmail account, but don't expect that feature to be too far down the road once they determine if people like the new application. According to the comments on the Google Code page, it doesn't look like too many people are upset -- most people have left comments similar to this:
YES quicksilver run by google! this happened in a dream once, except i was in ireland eating cake surrounded by scantly clad beautiful women
Once it's installed on your Mac, the search box can be launched by hitting the command key twice.