Skype will officially pull the wraps off its Apple iPhone application Tuesday, but it seems like every reporter with an iPhone got a look at the application over the weekend. Users will be able to Skype-inate over WiFi, including free calls to other Skype users and the whole cheaper calls bit via SkypeOut. A Skype version for the BlackBerry will appear in May.

PC World says that users won’t be able to place calls over a cellular data network; this is a protective sop thrown to the carriers so the app won’t (supposedly) diminish long-distance and roaming minutes. Presence and IM work the same and go over whatever data network is available; cellular or WiFi.

Skype for iPhone will use phone numbers directly from the iPhone’s address book and will also helpfully display Skype contact photos. Conference calling is available, but right now, an iPhone user has to be invited in.

Other features not available in the first version of Skype for iPhone are SMS, video, file transfer and voicemail. However, iPod Touch users will also be able to load and use Skype.