I upgraded my iPad2 a little while ago, 8.1, and Safari was worse, slower and more unresponsive than 8.01 or 02. Thought it was rendered totally unusable. I restarted, or I should say I tried restarting, stared at the apple for over 10 minutes and had to run out. Came back and it was up. It's now about equal to pre-8, Safari speed. Still things about Safari I don't like, but I can live with it now. I'm not planning on a new Air2 for about 2 months, and it will probably be an Xmas gift. Anyway, 8.1 is much better on my iPad that the previous 2 upgrades.
Edit: I just shut it off, waited about a minute, then started up. It was back up in less than a minute. Even though the installation restarts, I think a regular restart may be needed.