When you upload files to Google Docs, you'll notice a new option that tells Google to convert the text from PDF and image files to Google Docs documents. The feature has been released last year as an experiment, so Google had enough time to improve the accuracy of the results.
I've tried to convert an excerpt from the book Rework and the result wasn't great. About 10% of the text has been incorrectly converted and the formatting hasn't been preserved.
He compares his results to to ABBY Online as well.