I've seen how wheels are built that do not have spoke holes. Basically, the wheel builder feeds a cable in where the nipple will go, and out the valve stem hole. The nipple is then fed to the hole down the cable to the hole. This makes building the wheel very time consuming but has the advantage of not needing rim tape.
I'm not sold on the idea of doing it this way, mostly because if you break a spoke, it's not as easy to replace. I also don't believe there is much of a weight savings benefit since you normally would remove rim material and add tape, seems like it would be a wash.
So other than the extra labor involved in building the wheel, which it seems CarbonSpeed is willing to do for their customers, the only disadvantage would be increased difficulty if a repair is needed. Otherwise the only benefit is not needing rim tape and possibly holding air pressure better.