I think Google loves Twitter! You can see here how many accounts they have http://forums.digitalpoint.com/showthread.php?t=1414103
Twitter tweets will not help you get traffic on Google, but Twitter itself is a great way to get traffic to your sites.
I dont think that twitter does help in page ranking with Google mainly because any urls that you enter into Google are converted into short url form. So I dont really see how Google can pick up any relevant information to index a tweet properly. However, a log of business people seem to use twitter as a way of informing customers of say new goods and products.