I need to have my say on this one as well. I agree that the MMC based version would be *MUCH* more popular than the USB based version. I have a 1541 Ultimate for my C64 and it is a damn good product - so good in fact that i don't actually own any floppy disks anymore - and a similar device for the Amiga would probably mean the same thing (bare essential backups/originals)!
I have been waiting keenly for a production run of the MMC based version, but it seems runs of the USB version are what is happening. I suppose this is more aimed at those producing them to sell - why? Why o why?
*EDIT* - I just emailed the seller to ask "why?". We'll see what they say.