The famous tech site engadget has reported that the iOS 4.0.1 hitting iPhones right this second .It is not the full version of 4.01 but apple has taken some amount out of it. The site is currently testing the updates which is with improved formula of calculating the bars on the iPhone 4 and soon you will be able to catch the results of it.
There is an update from the site that it seems as iOS 3.2.1 for iPad is coming down the tube, as well
Here is the link of the site from where you can catch the download and install