You'll remember that we've gone over all the new features in Windows Phone 8.1 several times, most recently here. Plus many of us have been playing with IE11 in the 8.1 Developer Preview anyway, so it's very much a known quantity. But it's still useful to have a definitive 'what's new' list, here helpfully supplied by MSDN. Also, maybe there's a feature that you'd missed - take a look!

From the MSDN article:

You may have been hearing bits and pieces of news about IE11 on Windows Phone 8.1, and we’re excited to share the full scoop on user experience improvements with you today! Our team has been laser focused on delivering a massive upgrade to four key areas of your browsing experience: quick site access, fast and fluid browsing, safety and privacy, and accessibility.

Quick site access

Everyone always wants a faster browser, which is a fun challenge to work on - and our team breaks this down into two pieces. First, you need to tell the browser where you want to go, and second, the browser needs to get there as fast as possible. The second piece usually gets most of the attention, with browser performance benchmarks (like SunSpider, Acid3, Octane, and other muscular names) driving the discussion. While we have made progress on the benchmarks, a big focus this time was making serious progress on the first piece, telling the browser where you want to go. And here’s how we did it.

Frequent sites + URL predictions

When you tap the address bar, we know you likely want to go to a different site than the one you are looking at. We all have a few sites that we like to visit frequently, and those are now a quick tap of the address bar away. As you browse, these will update to reflect the sites you visit most on your phone. Here is a screenshot of mine.

 

If you decide to type in the address bar, we now predict the site you would like to go to (the highlighted part above). Instead of typing out the entire URL, you can just tap enter and be on your way faster. It is one of those things you can’t imagine living without once you have it. The result is a browser that just feels snappier, since it requires less work from you to get to your sites.

Unlimited (and easy to access) tabs + One IE, Everywhere

As more Web browsing shifts to mobile devices, we want to be able to complete more complex tasks on these devices. One example is multi-tabbed browsing. Previously, we only allowed up to six tabs and there was a small speed bump to access your tabs in the “…” menu (unless you used the setting to change the address bar button).

So we decided to remove this limit - seriously, you can open as many tabs as you like - and now the button next to the address bar accesses your tabs by default. Making tabs easy to access was a welcome change, yet we still heard requests for easy access to refresh. So we’re going to have our cake and eat it too. You’ll notice that the tabs button and refresh button are both immediately accessible.

  

If you’re an astute observer, you noticed the “other” pivot in the screenshot above. We are excited to announce that Internet Explorer 11 will sync your browsing data across phone, tablet, and PC. This includes your favorites, history, passwords, and open tabs. You can now quickly pick up where you left off when you switch devices, and finally say goodbye to emailing yourself links!

Heads up: if you are concerned about data use, we’ve got your back. Just enter your data limit in the DataSense app, and we’ll be smart about when to sync this data to help avoid data overage charges.

Live pinned sites

I love having quick access to my favorite blogs right on my start screen with pinned sites, but honestly, pinned sites have been super lame less than stellar thus far on Windows Phone. With just a static screenshot, they were second-class citizens next to the beautiful and dynamic live tiles from my favorite apps. That all changes now. If you have used Windows 8.1, pinned sites will now feel very familiar.

Pinned sites now show rich site icons and even update in the background, with the latest headlines and images from your favorite blog for example, just like other live tiles. If you own a Web site, you can find instructions on how to light this up for your site here (hint: exact same markup as Windows 8.1). If your favorite sites don’t support live pinned sites, point them at those instructions and let them know all the cool kids are doing it. We’ll be posting more details for developers but in the meantime check out this start screen made exclusively with live pinned sites.

The article goes on in the same depth. Summarising the structure of the rest of the article will give you an idea:

Fast and fluid browsing

So now we’ve got you on your way to sites much faster. We also want it to be wicked fast to get and consume the content you care about. So we also made strides on speeding up your experience after you arrive at the site, with in-line video playback, Reading View, remembering passwords, swipe to go back and forward, and saving downloaded files.

In-line video playback

Reading View

Remembering passwords

Swipe to go back and forward

Saving downloaded files

Safety and privacy

We were the first mobile browser to introduce anti-phishing protection with SmartScreen Filter and we also added the DoNotTrack signal to address growing privacy concerns. We’re at it again with a few features to keep you protected while browsing.

InPrivate

DataSense High Savings Mode

Accessibility

At Microsoft, we take an inclusive approach to product design – ensuring we understand the needs of all our users. I’m pleased that IE11 supports high contrast mode, Narrator, and an override switch to allow zooming into all Web pages. Look out for a future post on the Windows Phone blog covering system-wide accessibility for details.

You can read the full article here, with more screens and more description.

IE11 is a pretty far reaching upgrade to Windows Phone's browser, but it's not perfect, as can be seen from comments around the web. In particular, when managing 'tabs', the current tab (i.e. the one you were just in) isn't highlighted in any way, plus as you move around tabs their order in the tab browser keeps changing, so you have to memorise roughly what each page looked like, in order to spot it again later.

Like the rest of Windows Phone 8.1, IE11 may be tweaked slightly before we all get over the air updates officially, there might still be time for the Internet Explorer team to respond to feeback. But do note that the browser is baked into the firmware/OS image and isn't patchable via the Store. Maybe this would be something for Microsoft to look into, given how fast browsers are updated these days?