+1. As much as I like the idea of managing everything from one place, Google's propensity to have crap-tier support and their other propensity to drop services with little warning means I've got no desire to even try this.
I hadn't considered Google's lack of commitment to their non-core services, but that's a good point. Over the years I've consolidated at Namecheap while several other providers shut down. For me, domains are a long-term service.
I'll stick with NameCheap. All else being equal, I prefer the vendor whose core business is the service I'm seeking. They can neither drop the service nor quintuple the price (a la Google AppEngine). Same reason I use DropBox.