I use REX weather all the time since the built-in weather is so flaky. I live in South Texas where we have the conditions for pop-up thunderstorms virtually all summer and so the live weather almost always has thunderstorms and lightening even when we have partly cloudy sky’s.
It is true the transitions are annoying, but at least the weather being depicted is spot on for that area. During the winter months, when thunderstorms are less prevalent, live weather, when it works, is better for showing the weather over a large area without the abrupt transitions.