Thank you! Tablets should already be supported, although you may need to disable Windows Ink for them to work properly on Windows (should be the same with Microsoft Surfaces). In the next version, you will be able to change the tablet driver being used from Pixelorama's preferences, without needing to disable Windows Ink completely. Pen pressure is also coming.
Unfortunately, we don't have a Microsoft Surface to test some specific controls, so if you have some specific changes/improvements in mind, feel free to let us know!