They work great

Detects and blocks trackers just as described. The issues are in the control page. The list for managing tracked URLs is unnavigable. It's so small that it takes ages to load them all in once you've accrued a lot (which you will because it's the internet). Then once you start editing them the list refreshes. Every time. This needs a serious overhaul, just for basic use.
I won't rate it any lower because the functionality is definitely good, but I can't go higher because of the UI.