Other than the constant lag from 8.1, the one other issue that drives me nuts is the stuck live tiles when you disable an app from background tasks. Apps such as Weave and Flipboard have no option to turn off live tiles. So when you turn off their background ability in battery saver, instead of reverting to their generic logo tile, they just freeze with the last article update when ot was turned off. Makes your home screen look like crap. So many devs use the live tile horribly and this is just one example. I can't tell you how many use the almost the same color font as the background of the live tile, or don't adjust what is being shown for the different size icons (making what is being shown horribly clipped).