22Jun/100
iPhone OS 4.0
Since it was made available last night, I updated my iPhone to the newest OS 4.0. It seems to work really well so far, but Apple didn't update any of the documentation links in Safari, so I had to read about how to use the new features elsewhere. Here is a good guide from Gizmodo that goes through the ins and outs of the newest update.
UPDATE: The Ars Technica review is actually more thorough.