Just because you don't like it, doesn't mean it necessarily sucks? *shrugs* I can see where it might be useful if you're not really sure what you're searching for, and try some different searches without pressing enter to see what comes up, while modifying your search until you get what you want. I'm not for instant gratification, so I left it off, but there ways it can be handy.
I mean, they do ask if you want to try the instant search. If you try it and don't like it, there's a little link next to the search-button that allows you to turn it off without going off the page.
Personally, I like that Google tries a lot of new things - they have good ideas and bad ideas, and once in awhile they have some really cool and interesting ideas.