Advantages
Skype for iPhone is easy to use and it mimics the iPhone interface. You can send and receive Skype instant messages wherever you go and you don't have to be on a Wi-Fi network, as you do with voice calls.

Another feature is the ability to designate a cell phone number as your caller ID. This is crucial, because so many people these days let calls from unidentified numbers go straight to voice mail.

Incidentally, you don't have to own an iPhone to make mobile Skype calls. Other formats are also available like Skype for Windows Mobile, Skype Lite for Java phones, and a version for Google Android phones.

Disadvantages
You have to be logged into Skype on your iPhone in order to receive an incoming call or instant message. Currently, you can join a Skype conference call but you can't initiate one on your iPhone. You can't add an emoticon to an IM or see one in a message you receive.

You can't video chat using Skype for iPhone although it might come soon. Currently, iPhone 3G doesn't support video recording, though there are some video recording apps you can download to a jailbroken iPhone.

Conclusion
If you own an iPhone and travel often, Skype for iPhone is recommended. Get your close business associates, family, and friends to install Skype on their computers and cell phones, too. You could call them from your Wi-Fi-equipped hotel room and talk for hours thus eliminating the need to find a computer to talk. And best of all, you won't have to worry about the bill when you check out of your hotel.