Now, several people have reported that the new floating toolbar causes their CPU usage to go up. So tsangk's proposal is a viable fix for that issue. Anyone with the CPU issue, please try tsangk's workaround, and report your progress either here or on that thread.
As for our official view on this: go for it! Your own desktop is your property. Use ad blockers or GreaseMonkey or anything else you need to tweak the look of your browser contents. However, please respect the way Wikidot serves these elements to other users.
Note also that if you hide your top toolbar, you won't get the new features we're adding. But it's your choice.