Sneaking in at the turn of the year is the latest update to the Paypal application. Picking up a number of bug fixes for Nokia Lumia users, the application still doesn't reach the dizzying capabilities of the iOS or Android versions, but if you're looking for an app to keep an eye on your account, and manage the flow of money coming in and going out, this should suffice.
Following on from v2.2, the app now supports Windows Phone 8 with double width and small sized live tiles. The first pass on a Windows Phone 8 version of the app had some compatibility issues with the Nokia Lumia 920, but these appear to be fixed in this version of the application.
The app is likely going to roll out on a region by region basis, so check the Windows Store for availability on your smartphone.