Last week I was surprised to see that Skype Mobile was not available yet even though I understood why however the wait is over for early adopters with the Skype Preview that is available in the Windows Phone Store right now. Because of the new capabilities of Windows Phone 8, this version of Skype is much more integrated with the Phone where it can now run in the background allowing you to receive calls and messages even if the app is not running. And of course if you have linked your Skype Account to your Microsoft account you can login with either username and password combination.
Another really cool feature and signs of deeper integration is the Skype hook into the People Hub. Also you will find your Skype Contacts integrated into the Windows Phone People Hub where you can initiate calls and even link your Skype contact with their other contact info if it exists.
If you are going to grab the Skype Preview keep in mind that it is an early build and there are of course know issues which have been listed out on the Skype blog. Some of the issues include incoming calls coming in over cellular when the screen is off and not switching over when activated and not being able to switch between the front and rear camera. You can see the full list of bugs on the Skype Blog.
Grab a copy of the Skype For Windows Phone 8 Preview in the store.