Absolutely essential to browsing the web. It's the fastest, best, and most powerful, there is zero reason to install any adblocker other than this one (because it's not _just_ an adblocker).

But for adblocking... the default settings are fine, but the real bread & butter is with the extra filter lists. uBO -> Open the dashboard (settings) -> Filter Lists, enable all of them, _especially_ the annoyances. And for power users and paranoid folks, there's medium mode and the ability to block JS and such.