Perfect for the users, for whom uMatrix is too complex or granular.

5 stars even though:
- it constantly loses some settings (such as advanced mode and cloud support) upon restart; a button to „show advanced mode panel“ would be a nice workaround and addition: really, for most users it is only needed occasionally;
– I'd like to have more control of cloud account – for transferring between browsers, e.g., or privacy issues (where are the settings stored? how the profiles are identified on the backend – this feature sorta breaks the presumption of full control over the web and tracking);
– I'd like to have an option to define my own script surrogates: many sites may be fixed just by defining a mock object such as Gemius={ player: { play: ()->undefined, stop: ()->undefined, ...}, init: ()->Gemius };
– it duplicates and, to some extent, clashes with Firefox'es internal tracker protection and such innocent extensions as DuckDuck privacy extension or ToS;DR which use the same default tracker lists; it would be very nice if uBO respected the settings of Firefox itself: if I whitelist a site in the default tracker, I'd like that those exceptions also propagated to uBO;
– the UI is absolutely counterintuitive;
– I feel it interferes with with GreaseMonkey clones and bookmarklets, but haven't done any in-depth research: on the contrary, I feel it would be nice if one could define someSite<->javascript: CSP rules in uBO.

And in general, uBO has a huge codebase of near-perfect request interception and redirection. It has a huge potential for geeks if there was some point to attach callbacks. For example: intercept and redirect .doc files to Viewer.js or Google Docs if content-type matches and it does not come from Google Docs :)