The prototype 350 I did last year was just that.  It was never viable for anything off the bench but it was a great learning platform.  The R1 is meant to be a refinement that actually works:

• Fits in a commercially available enclosure
• 350 watt (VA) output
• 11-16V DC input
• Semi-regulated output 110~120V AC RMS
• Distortion on par with commercial units (<5% THD)
• Powers wide variety of small appliances - resistive, electronic, inductive
• Operates in ambients up to 50C
• Lower EMI floor than prototype

It mostly meets these.  Two problem areas are dissipation and poor regulation at high loads (low output voltage).  Neither are show stoppers and its another opportunity to learn & improve.