I think the difference between the two is that you'd have been logged into Firefox on an account with the beta turned on,and either logged off on IE, or else on a different account!

You'll probably need to slightly adjust your CSS to account for the new HTML structure -- we have someone looking into making things work for official layouts; it might be useful to wait for thoes and base your changes upon them!

Re: hover menu it's actually a deliberate thing. If you hold your mouse over the icon rather than moving it away at once, then it'll show up. (This is to account for someone scrolling down the page where their mouse goes over an icon, where they don't really mean to get the icon, they're just trying to go through their read page)