I just did it and it was a lot easier than I thought. It's pretty automated, and USCIS put a decent system in place.

The only trouble I had was selecting my arrival and current status. In the past, I would write in "Unlawful" but the option for that is now "No Lawful Status" as I wrote in this post with more online renewal info.

It took about five business days for them to approve the case. The receipt notices took longer to arrive! Probably my fastest renewal yet.