It's a good machine, except for it exclusively using firewire as its transfer protocol. This, more than anything else, seems to be causing issues for many users (including myself).
For these users, the internal chipset of their desktops and laptops appear to be less than 100% compatible with the MR816's FW driver, and Steinberg recommends only using FW cards that have a TI (Texas Instruments) chipset - check their website for a list of manufacturers.
So this is a digital audio company selling interfaces that don't work properly with several types of popular PC and Mac chipsets, and telling their customers that their computers have bad parts that need to be replaced.
I have no idea why Steinberg/Yamaha chose FW400 over USB 2.0 (there is little real world difference in transfer speed), but I'm guessing the number of returned units so far will have them reconsidering this decision for future models.