One current weakness with the call handling abilities of this iPhone client is that you can't setup multiparty calls. This is a bit bizarre because you can actually join a multiparty call if someone else invites you. Multiparty calling is useful because it allows you to create spontaneous teleconferences with multiple work colleagues or just to get everyone on the line to agree a time to meet in the pub. Naturally you can start a multiparty text chat session, but it's not quite the same thing is it?
Speaking of the chat feature, unlike voice calling you can use it over the EDGE or 3G network so at least you can chat via text with your mates when you're out and about. However, one annoyance that we noticed is that the chat keyboard can't be re-orientated into landscape mode, which would have made tapping out messages a little bit easier. There's also no support for file sharing at present, which is a tad limiting if you use Skype for work purposes.
On the plus side there are a few features that are currently exclusive to the iPhone version. For example, you can take a picture directly from within Skype and use it as your avatar or alternatively select an image from your existing photo library.
Overall, though, Skype on the iPhone isn't quite the revelation that we expected it to be. The biggest issue is simply the fact that it can't be run in the background ready to receive incoming calls. This means that Skype callers will potentially have to email you or call you via the normal mobile network to tell you to run up the application, which kinds of defeats the purpose of the whole thing. It also puts the iPhone version at a serious disadvantage to other versions. However, this is likely to be cured when the new V3.0 iPhone OS is released later this year.
The other major downer is the current lack of support for making voice calls via EDGE or 3G. Again this may change in the future, but it will not just depend on support for it in V3.0 of the iPhone OS, but also the willingness of carriers like O2 to allow the service to proceed unhindered - something there's no guarantee of because it has the potential to eat in to their core call revenues.
Although this version is very useful when you want to make cheaper calls abroad, and blends in beautifully in terms of design with the iPhone's own mobile calling features, it's definitely not the best version of Skype on a mobile phone.