Earlier today there was discussion of the FluxEngine[1], due to it's newly added Mac 800k disk read/support (OK, it had read for a while, but now it can both read and write).
What I love about the FluxEngine is that it is so simple - no custom PCBs, just a single PSOC development board with a single set of soldered header pins.
Not saying that the other alternatives are bad - it's great to have competition. For several years it seemed that KryoFlux would be the sole dominant USB floppy controller, nice to see there's a range of options available.
Edit: seems as though FluxEngine may gain support for using GreaseWeazle hardware[2] at some point, which would be neat!