How well does iPhone/iOS work with Microsoft services?
I don't actually know a lot about Windows Phone, but I would think that the biggest issue you might face would be with Skydrive. There is an iOS Skydrive app, but like all iOS apps, it is sandboxed. So you don't automatically have access to files on Skydrive unless the other app you're using either implements the API to connect to Skydrive directly or registers in the system as an "open inů" target for various file types (ie - in the Skydrive app you select a file and choose to open that file in a different app. However with "open inů" a copy of the file is made in the receiving app and updates would not be made to the file version on Skydrive. To have updates reflected to Skydrive you would need an app that implements the Skydrive API.
The above may or may not make any difference depending on your workflow and current use of Skydrive.
Skype would be fine. There is an iOS app.
Mail would be fine assuming that outlook.com can be set up with Exchange, pop or imap.
You should be able to use iTunes on the classic side of Win8 although in a lot of cases there is no need to ever connect the phone to a PC or Mac.