Nice review.  I currently have the old iDSD and the Dragonfly Red.  They perform very close to one another, but the Dragonfly Red is only $200.  I'm having a hard time justifying the extra cost of the iDSD.

I haven't found any DAC that supports DSD over coaxial or optical natively. In my experience DoP or conversion always has to be used. The Mojo, for example converts everything to PCM--it doesn't do native at all. Therefore, I think your one negative is probably a bit unfair. I think there is a firmware flavour that does DoP, but why compromise the sound?
 
With regards to Dragonfly Red, it only plays to 24/96, doesn't do DSD, and has a weak-sauce amplifier compared to the iDSD. If you don't need DSD, PCM above 24/96 or a powerful amp, then the iDSD is probably overkill for you.