[dedward]

Even for fast typists - speed and response time affects your perception of the site subconsciously. The faster and more realtime it seems the more you are going to like it, even if you aren't sure why, or don't even think about it. You may not even realize why if asked why you like it better - but the statistics and studies are there and are solid - so this is likely a very good move on google's part.

[uxp]

The first few searches I queried google for this morning didn't have this instantaneous result feature. This afternoon, it did, but I didn't notice it until I actually became frustrated when I would change a query and click "search", and the results didn't change. It took me a minute to actually notice how the results were dynamically changing under me.

It may take a day or more to get used to, but it really does speed up the workflow.