I think his good shooting is potentially a plus, but that he needs much more experience at understanding what he needs to do to get off a good drive or good shot. He appears to be mostly relying on quickness alone, instead of closely watching the defender and taking advantage of the defender being off balance or too far away to be effective. I'm not explaining my thought well -- he seems to just be hoping that "blind quickness" will be sufficient. He will be much better if he can learn like Andre Miller, to selectively use quickness when it counts.
I couldn't really tell whether or not his foot speed was good enough on defense, but it seemed that he has a ways to go before he can be at all effective on the defensive end. He looks to be too light, too slow to jump, and not willing to be proactive on the defensive end. My sense is that it will take at least one more year to determine if he can ever play defense, without being a real liability.
I couldn't really tell whether he can run an offense or not.
In my own mind, my hopes increasingly are focused on PKoppenen. This seems to be an era of few decent point guard. Passing on both DWilliams and CPaul is increasingly looking like monumentally poor scouting/judgement. I guess, unlike you, I see SBlake as probably the best obtainable option out there for a backup (underline that word) PG for any real push forward the next two years. That still would leave a vacuum in the future when Andre is out of gas.