I???d probably give the app 5/5.
I don???t really like Fluxx. It can be mildly amusing with my kids but there is really no strategy, there is a ton of randomness, and the game can sometimes drag on forever.
That said, the app is a perfect recreation of the card game. It is bright and lively, it implements Playdek???s perfect asynchronous multiplayer (which every developer out there should strive to emulate), and as a bonus, Playdek has updated the app not just to be 64-bit, but to fit the newest iPad/iPhone aspect ratios.
My perspective is different, because as a game Fluxx maybe gets a 2/5 for me. I know that already, though, so my review approaches the app purely based on how well it digitally represents the card game it is based on.