Following up on rumors, Apple has released iOS 4.0.1 via iTunes. Per MacNN, the update makes just a single major change, that being improved accuracy in iPhone signal display. The company recently promised a software fix in light of reception issues, though it’s now believed the problem is traceable to hardware. The download is only available for the iPhone 3G, 3GS and 4.

For iPad owners, Apple has meanwhile posted iOS 3.2.1. The firmware solves several issues, most notably trouble with Wi-Fi connections. It also corrects a glitch with PDF attachments in Mail, and two video bugs: one causing videos to freeze, and another hampering the official iPad Dock Connector to VGA Adapter. The one feature addition is Bing support for Safari search.

To download and install the updates, which each weigh in at over 300 megabytes, attach your iPhone or iPad to your computer, open iTunes, select the device and search for an update. The process will occur as per usual.

Apple is scheduled to hold a full iPhone 4 press conference today. Stay tuned to the PowerPage for additional details as they become available.

And if you’ve noticed any major changes or would like to offer feedback on this, let us know.