I've recently tried to switch back from chrome to Firefox but the persistent search thing really bugs me, as well as the fact that it doesn't always search when typing into the url bar.

If you want to get back so quickly there are recently closed, bookmarks, history and plenty of other ways. Always persisting the search term I find very visually distracting.

Edit: On the other hand, the current tab behaviour is more of an irritation. Middle clicking the tab closes the tab unless it's the last tab when it does nothing. This is irritating. Dragging a tab doesn't work well when that tab is maximised. In chrome if you have 2 windows both maximised it's easy to drag a tab from one window to the other. In firefox you have to make one window smaller first to do this.

I'm quite excited to find out if this new interface fixes this.