The lag in swiping back in IE depends largely on the site your viewing. For example, this site works great but other sites like gizmodo take a bit to refresh after swiping back.
As for WiFi, the 8.1 is better for me. After connecting at work, I would always be limited to ~1MB down (still get 14MB up) until I opened the wifi adapter settings, toggled some setting and re saved it. Then it would work fine. After the 8.1 update, this is not required anymore.
Finally, a big change that I noticed is that 8.1 remembers where you were at when you close a metro app. For example, if you are on the desktop and you view a jpg, the metro photo viewer opens up. In 8.0, when you swiped down to close the viewer, you went to the start screen. With 8.1, you go back to the desktop. This is very welcome.
Also, it turns out my printers were there after all. They just don't appear unless they are actually connected.