re: storage and OS
storage:
1. I expect storage on our smartphones to grow rapidly in the near future, so an external drive isn't as much of a big deal.
2. Storage is far from "the only really big advantage" that a PC has. The biggest problem with smartphone hardware that prevents me from using it as more than a cellphone and a toy is its input interface. My smartphone's keyboard sucks for text input. It's better than the keyboard capabilities of almost any other smartphone available (and that's probably the biggest reason I bought this particular device), and it still completely sucks.
OS:
I'm not sure what you're saying about letting hardware manufacturers make their own OS. Android is one of Google's OSes.