I love the new native ui FF. Not so much the actual interface (it being so damn fiddly with its tiny X's to close tabs instead of swiping and the stop/reload button being located in the url bar) but for its speed. It opens and loads pages really quickly. Faster than Chrome, it seems.
The biggest problem it has is it isn't very good at page formatting. In particular, tap to zoom or pinch to zoom. Tapping seems to have two levels: one, it zooms out as far as possible to show the entire page at the developers prefeffered width, or two, zooms in to a specific div until it marches the scren width. The later sometimes works depending on the html, but most often doesn't make text large enough. Pinching lets you zoom pretty arbitrarily, but treats the page simply as a canvas with no effort to reflow text.
Opera is the best when it comes to formatting since it freely breaks lines and reflows text after pinching to zoom (the only browser I've seen do that).
The upcoming reading mode should help but I dont want to have to change modes just to be able to read a page.