I was going to, but their pricing is not kind if your portfolio sits just above one of their limits. So I've either got to buy more or sell more to make it worthwhile.
Plus, by signing up, wouldn't you automatically pay 25% at GoDaddy-owned venues?
Also, I think the service is a LOT less useful now that GoDaddy has killed Uniregistry and started amalgamating the domain marketplaces under a constant 15/25 commission model. Fewer real competitors make it less likely for me to sign up.