Updated April 3, 2009 at 11:00 am PT with more questions and answers.
I'm going to answer some of the most frequently asked ones here, but if you've got more, you know what to do. Put 'em in the comments.
First of all, some context. Skype for iPhone is a voice over Internet Protocol, or VoIP, communications application that lets you chat with other Skype members for free, plus call landlines and mobile phones when you buy Skype Out credit. It is available in every country in which the App Store can be found, and it has already made a splash in the United States, Japan, and Europe.
Apple requires Skype and other voice applications to use Wi-Fi to place iPhone calls, not the hardware phone. Now without further ado:
1. If you've already got an iPhone, what's the point of having another calling application?
At least at first, Skype was primarily used to place international calls for free to other Skype users, or to landlines at a reduced rate on par with a calling card, for example. If you've got family and friends living abroad, the application's potential is a no-brainer.
Sure, you might not need to use Skype if everyone you know and love lives within a 500-mile radius of you. Yet users have already chimed in with examples of domestic uses, like if your home has a weak cellular signal but strong Wi-Fi; or if you eat through your free-talk minutes, a low-rate VoIP service like Skype will cost you less than the carrier's charge for each minute you go over your plan.
Also, don't forget that iPod Touch owners can use Skype and other VoIP applications (like Truphone and Fring) to make calls, even though the iPod has no telephone hardware--you just need earphones equipped with a mic.
2. If you're on the road, you still can't use your iPhone to make free calls with Skype, unless you can track down a Wi-Fi connection somewhere.
If you're in the United States, AT&T allows iPhone users free access to AT&T hot spots without incurring extra charges, though if you're attempting a call, you might not want to start it in the middle of Starbucks.
Also, even when you've got a laptop or desktop handy, and could use VoIP on the desktop, a calling client on the mobile phone gives you the freedom to wander. You won't be able to see your pals with the Webcam from the iPhone, though, so there is a trade-off.
3. Does Skype for iPhone use the native iPhone address book or a proprietary one?
Skype hooks into your iPhone's address book from the dialing screen so you can easily call a non-Skype buddy using Skype credit you've purchased. The Contacts screen shows your list of Skype contacts, and it's from here that you initiate a chat or call to Skype pals who aren't in the phone's address book.
4. Will Skype for iPhone notify me of missed messages or calls when I am running other apps, or when the iPhone is inactive?
Yes and no. You'll see notification circles of a missed message or call on the separate screens when you've got the app running, and again on the program icon, if you close the application with unread chats. Yet since Apple doesn't let you have more than one application running at a time with iPhone 2.0 software, you won't get an alert, if you're using another app and someone tries to reach you (you'll appear offline to them, anyhow.)
Even if you do see a notification alert on the program icon after you've closed Skype, the number of missed calls you see won't update to reflect the current number until you sign back into Skype.
5. Can you receive calls from your SkypeIn online number when you're in a Wi-Fi hot spot?
Yep. If you've already purchased a SkypeIn number, the service should work seamlessly on the iPhone without extra activation steps.
6. Do you need a headset to make a call?
On the iPhone, you'll be able to hold the phone up to your ear as you would when using the phone, though the application is also compatible with a headset and with speakerphone. Note, though, that you will need a microphone-equipped headset when using Skype with the iPod Touch.
7. Does the new Skype for iPhone allow you to make video calls?
No, it doesn't. This is a feature that Skype hasn't appeared to have figured out. The technology is out there, however. One company, iVisit, has been showing its video conference call technology for at least the last year. Rest assured, video Skype will be huge news when it comes out, on any mobile platform. Mobile video is so essential these days, that whichever VoIP app manages to get there first will undoubtedly get all the glory.
8. Can you also forward your mobile calls to your Skype-In number? If you can, presumably you can avoid time charges from your mobile carrier by making and receiving all calls with Skype as long as you're somewhere where you can get a Wi-Fi signal.
This wouldn't actually work in your favor on the iPhone if you intend to use the device for anything other than waiting to receive a call. Remember that Skype is only active when you're signed in, and cannot run in the background due to Apple's rules and regulations in its version 2.0 software. My impression is that most people will use Skype for iPhone to dial out, either when they've got a phone date planned, or when there's a chunk of free time to call a friend while out and about, perhaps while waiting at the airport, for example.
9. I want to consider using Skype, but I want to use it for calls when I'm in Italy--will it work from one location in Italy to another in Italy? And what number does the caller use to call me back, my U.S. iPhone number? If so, the caller would end up with international cell phone charges.
What I understand is that you have a U.S. iPhone and want to travel to Italy to make a call within Italy? AT&T would charge you an arm and a leg, so you want to use Skype over Wi-Fi to avoid those charges and to avoid buying a local or international phone card. If I got that right, in theory, you should have no problem initiating a call from Italy to an Italian landline (calls to mobile phones will cost more.)
The sticky spot comes when you want your pal to reach you. The most cost-effective solution is for your buddy to also sign up for Skype. Failing that, you could also pay for a Skype-In number for your friend to contact you, but see Question 8 for complications. If you want to be cost-conscious with your contact, I might try other communication avenues--instant messaging, IM, and e-mail, all which you can easily check on iPhone while doing other things. There's always the low-tech way of doing things--your contact e-mail or IMs you to let you know they're ready for that call.