Something that hasn't been mentioned yet is the ability to block advertisements. This is useful for many reasons:

1. First and foremost, ads can give you malware. While this isn't as prevalent on mobile devices, incidents have occured of advertisements on websites giving the user malware, even on high-profile sites like Forbes. studies have shown that ads are 182 times more likely to give you malware than porn websites.
2. Ads slow down the page load and cost you time, sometimes even scrolling the page in your place because an ad that's loading shifts content up or down.
3. Downloading ads costs bandwidth. It has been estimated that ads can take up close to 40% of the bandwidth of a page you're downloading. For mobile users with a limited cap, this can be particularly impactful.
4. Ads tend to be obnoxious, with autoplay videos, autoplay sound, wildly moving images, pop-ups, pop-unders, ads expanding to fill the page, gaming ads that are just images of big titties with a "play now" button,... People have been sent to detention because their mobile phone suddenly started playing a video ad while their phone was in sleep mode. I personally once got a 21 minute ad on a 16 minute video on Youtube.

Now, Apple didn't just add an adblocker into ios 9, but they added the option to block certain content. https://www.hackingwithswift.com/safari-content-blocking-ios9-install explains how to install the most popular one on the market.