I just love this explanation of partial classes from devx:

One of the greatest benefits of partial classes is that it allows a clean separation of business logic and the user interface (in particular the code that is generated by the visual designer). Using partial classes, the UI code can be hidden from the developer, who usually has no need to access it anyway. Partial classes will also make debugging easier, as the code is partitioned into separate files.

Yeah, so long as we keep the UI and domain code in separate methods in the same class, we've achieved real separation. Someone fetch the clue by four...