I've received confirmation from Wacom that they are aware of the issues introduced by version 126.96.36.199 of the Feel driver, released in mid-February.
As many of you noticed, the driver disables the volume buttons on the Surface Pro 1 and 2. Additionally, it uses too much CPU which can cause a delay in the cursor movement in some applications on less powerful devices.
"We tracked the problem to an expensive API call that someone slipped in (the culprit has been punished)," writes my Wacom contact.
Some other minor bugs are being ironed out and a new build should be available within two weeks. For now, your best bet if you're affected by these issues is to uninstall version 188.8.131.52 and revert to one of the legacy Feel drivers located here.