The news media are reporting that Skype will indeed be released for the iPhone on Tuesday, March 31. An interesting article in the New York Times explains that you won't be able to use Skype via your data connection because AT&T is worried that callers will use Skype rather than their voice minutes, which are more profitable for the carriers. So Apple limits Skype and other IP telephony apps to Wi-Fi. PC World has a detailed overview, including screen shots.
CNet gives some info about the app's features. These include taking advantage of the iPhone's ability to use filters to sort contacts, chat, taking a photo from within Skype to serve as an avatar image, and the ability to mute a call, put it on hold, or or put it on the speakerphone.
Update 4/2/09 Here are a couple more reviews:
Here are a couple more reviews: