Excellent ad-and-other-annoyances blocker. It's simple to set up but you can also dig around and configure a lot of the rules if you need to.
Things I most like about this: easy blocking of annoying (and slow) JavaScript and social media buttons (which are redundant since you can just share with the iOS share button). Great stuff.
A final note: I noticed another reviewer suggested this was useless in the UK. I'm in the UK and it works on the UK sites I visit, even without adding custom rules.